Q.1 Which type of amplifier is primarily used to amplify low‑level bioelectric signals such as ECG with minimal distortion?
Voltage follower
Operational amplifier in single‑supply mode
Instrumentation amplifier
Differential amplifier with high CMRR
Explanation - Instrumentation amplifiers provide high input impedance, high common‑mode rejection, and adjustable gain, making them ideal for biopotential measurements like ECG.
Correct answer is: Instrumentation amplifier
Q.2 What is the main advantage of using an instrumentation amplifier over a simple differential amplifier?
Lower power consumption
Higher gain‑bandwidth product
Superior common‑mode rejection ratio (CMRR)
Simpler circuit design
Explanation - Instrumentation amplifiers incorporate internal resistors to match input impedances, resulting in CMRR values of 80–100 dB, much higher than typical differential amplifiers.
Correct answer is: Superior common‑mode rejection ratio (CMRR)
Q.3 In a typical ECG front‑end, why is a low‑frequency cutoff around 0.05 Hz used?
To eliminate high‑frequency muscle noise
To prevent baseline wander and DC offset
To allow the QRS complex to be captured
To match the bandwidth of the display unit
Explanation - A high‑pass filter with a cutoff around 0.05 Hz removes slow variations in the signal, reducing baseline drift while preserving the ECG waveform components.
Correct answer is: To prevent baseline wander and DC offset
Q.4 What is the typical input bias current of a low‑noise op‑amp used in bioamplifiers?
10 µA
1 µA
10 nA
1 nA
Explanation - Low‑bias current (≈10 nA) reduces offset voltage drift caused by input bias currents, which is crucial for sensitive biopotential measurements.
Correct answer is: 10 nA
Q.5 Which filtering technique is most effective for removing 60‑Hz power‑line interference from an ECG signal?
Notch filter
Low‑pass filter
High‑pass filter
Band‑stop filter at 60 Hz
Explanation - A narrow band‑stop (notch) filter centered at 60 Hz attenuates the line interference without affecting neighboring frequencies.
Correct answer is: Band‑stop filter at 60 Hz
Q.6 Which configuration provides the highest input impedance in a bioamplifier design?
Voltage follower
Instrumentation amplifier
Differential amplifier
Inverting amplifier
Explanation - Instrumentation amplifiers typically have input impedances in the GΩ range, far exceeding other configurations, minimizing loading of the biopotential source.
Correct answer is: Instrumentation amplifier
Q.7 What is the purpose of a guard electrode in a bioamplifier circuit?
To provide a reference voltage
To shield the input from external noise
To bias the input transistors
To increase bandwidth
Explanation - A guard electrode is driven at the same potential as the input electrodes, reducing leakage currents and shielding the high‑impedance inputs from interference.
Correct answer is: To shield the input from external noise
Q.8 Which parameter of an op‑amp directly influences the signal‑to‑noise ratio (SNR) of a bioamplifier?
Bandwidth
Input offset voltage
Input noise density
Power supply voltage
Explanation - Lower input noise density leads to higher SNR for biopotential signals, which are inherently low amplitude and noisy.
Correct answer is: Input noise density
Q.9 In an instrumentation amplifier, the gain is set by which of the following resistor values?
R1 and R2
R3 only
R2 and R3
R1 only
Explanation - The gain is given by 1 + (2R2 / R3) in typical 3‑op‑amp instrumentation amplifier designs.
Correct answer is: R2 and R3
Q.10 Which type of noise is most significant in electrode‑skin impedance variations?
Johnson (thermal) noise
Flicker (1/f) noise
Shot noise
Electrochemical noise
Explanation - Skin‑electrode interfaces generate electrochemical noise due to ion exchange and motion artifacts, impacting the biopotential measurement.
Correct answer is: Electrochemical noise
Q.11 A differential amplifier with a gain of 100 and a CMRR of 80 dB will exhibit how much residual common‑mode gain?
0.01 × gain
0.001 × gain
0.1 × gain
1 × gain
Explanation - 80 dB CMRR means common‑mode signals are attenuated by 10^4 (i.e., 0.01 of the differential gain). With a gain of 100, residual common‑mode gain ≈0.1.
Correct answer is: 0.001 × gain
Q.12 What is the typical bandwidth (−3 dB) of an ECG front‑end amplifier?
0.1 Hz–150 Hz
1 Hz–100 Hz
0.05 Hz–40 Hz
0.5 Hz–200 Hz
Explanation - Clinical ECG signals contain components up to about 150 Hz; a bandwidth of 0.1–150 Hz preserves the waveform while rejecting high‑frequency noise.
Correct answer is: 0.1 Hz–150 Hz
Q.13 In a biopotential amplifier, which component is commonly used to stabilize the supply voltage and reduce power‑line ripple?
Zener diode
LC filter
Voltage regulator
Decoupling capacitor
Explanation - Decoupling capacitors placed close to op‑amp pins smooth supply voltage fluctuations, minimizing ripple that could be mistaken for bio signals.
Correct answer is: Decoupling capacitor
Q.14 Which of the following is a common source of motion artifact in EMG recordings?
Cable bending
Temperature drift
Electrolyte depletion
Ambient light
Explanation - Mechanical movement of cables relative to electrodes changes electrode impedance, introducing low‑frequency noise seen as motion artifact.
Correct answer is: Cable bending
Q.15 Why is a high input impedance necessary for a bioamplifier?
To minimize power consumption
To reduce the need for shielding
To prevent loading the biopotential source
To increase bandwidth
Explanation - Biopotential sources have high impedance; a high‑impedance amplifier does not draw current and thus does not alter the measured signal.
Correct answer is: To prevent loading the biopotential source
Q.16 Which of the following is NOT a typical feature of an instrumentation amplifier used in a medical device?
Adjustable gain
Built‑in low‑bias current
Low output impedance
High slew rate
Explanation - Slew rate is not critical for low‑frequency bio signals; low noise and high CMRR are more important.
Correct answer is: High slew rate
Q.17 What is the main reason for using a differential input stage in ECG electrodes?
To increase the signal amplitude
To cancel out common‑mode noise
To provide a reference to ground
To simplify the circuitry
Explanation - Differential inputs reject common‑mode signals (e.g., 50/60 Hz interference) common to both electrodes.
Correct answer is: To cancel out common‑mode noise
Q.18 Which of the following best describes the function of a shielded cable in biomedical instrumentation?
To reduce cable capacitance
To provide mechanical strength
To prevent electromagnetic interference
To increase bandwidth
Explanation - Shielded cables contain a conductive layer that blocks external EMI from coupling into the signal path.
Correct answer is: To prevent electromagnetic interference
Q.19 In a bioamplifier, the term 'offset voltage' refers to:
The maximum output swing of the amplifier
The difference between the two input voltages required to zero the output
The amount of noise added by the amplifier
The voltage at which the amplifier saturates
Explanation - Offset voltage is the input differential voltage that causes zero output; minimizing it is crucial for accurate biopotential readings.
Correct answer is: The difference between the two input voltages required to zero the output
Q.20 Which component is used to implement a DC block (high‑pass) in a bioamplifier front‑end?
Resistor
Capacitor
Inductor
Transformer
Explanation - A coupling capacitor blocks DC while allowing AC signals to pass, forming a high‑pass filter.
Correct answer is: Capacitor
Q.21 The noise figure of an amplifier is defined as:
Ratio of input to output noise power
Ratio of output to input noise power
Power spectral density of the noise
Minimum noise voltage per square root hertz
Explanation - Noise figure quantifies how much an amplifier degrades the signal‑to‑noise ratio compared to an ideal device.
Correct answer is: Ratio of output to input noise power
Q.22 Which of the following is a typical gain value for the first stage of an ECG front‑end?
1–5
10–100
200–500
1000–2000
Explanation - The ECG signal amplitude (~1 mV) requires moderate amplification (10–100×) before digitization.
Correct answer is: 10–100
Q.23 Why is a low‑noise op‑amp preferred for EMG signal acquisition?
Because EMG signals are high amplitude
Because EMG signals are low frequency
Because EMG signals are low amplitude and noisy
Because EMG signals are sensitive to temperature
Explanation - Low‑noise op‑amps ensure that the small EMG signals are not overwhelmed by the amplifier's own noise.
Correct answer is: Because EMG signals are low amplitude and noisy
Q.24 What is the main advantage of using a fully differential ADC in biomedical instrumentation?
Higher sampling rate
Better noise immunity
Simpler PCB layout
Lower cost
Explanation - Differential ADCs reject common‑mode noise, which is abundant in biomedical environments.
Correct answer is: Better noise immunity
Q.25 Which parameter determines the low‑frequency cutoff of a high‑pass filter formed by R and C?
f = 1/(2πRC)
f = 2πRC
f = RC
f = 1/(RC)
Explanation - The -3 dB cutoff frequency for a first‑order RC high‑pass filter is f = 1/(2πRC).
Correct answer is: f = 1/(2πRC)
Q.26 In a biopotential amplifier, the term 'bias current' refers to:
The current supplied by the power supply
The small leakage current entering the input terminals
The current through the gain resistor
The current flowing out of the output
Explanation - Input bias current is the current that must flow into the op‑amp inputs; it can cause offset errors especially with high source impedance.
Correct answer is: The small leakage current entering the input terminals
Q.27 Which of the following is a key design consideration for the electrode–skin interface?
Low impedance and stable contact
High impedance to reduce power
High noise to improve sensitivity
Fast switching to increase bandwidth
Explanation - Stable, low‑impedance contact minimizes motion artifact and ensures accurate biopotential measurement.
Correct answer is: Low impedance and stable contact
Q.28 Which filtering technique is commonly used to isolate the QRS complex in ECG analysis?
Band‑pass filter (0.5–40 Hz)
High‑pass filter (5 Hz)
Low‑pass filter (10 Hz)
Notch filter (50 Hz)
Explanation - A band‑pass filter between 0.5 and 40 Hz preserves the QRS complex while rejecting low‑frequency drift and high‑frequency noise.
Correct answer is: Band‑pass filter (0.5–40 Hz)
Q.29 What is the primary function of an anti‑aliasing filter in an ADC used for biopotential signals?
To increase the ADC resolution
To limit the bandwidth before sampling
To reduce the power consumption
To compensate for temperature drift
Explanation - Anti‑aliasing filters prevent higher‑frequency components from folding into the sampled spectrum, ensuring accurate digital representation.
Correct answer is: To limit the bandwidth before sampling
Q.30 In instrumentation amplifier design, the resistor matching tolerance directly affects which of the following?
Power consumption
Noise figure
CMRR
Slew rate
Explanation - CMRR depends on the ratio of resistors; mismatches degrade common‑mode rejection capability.
Correct answer is: CMRR
Q.31 Which of the following statements about the signal‑to‑noise ratio (SNR) in biopotential measurement is true?
Higher gain always improves SNR
Noise is independent of the input impedance
Low‑noise op‑amps improve SNR
SNR is not important for ECG signals
Explanation - Using op‑amps with low input noise reduces the additive noise, thereby improving the overall SNR of the measured signal.
Correct answer is: Low‑noise op‑amps improve SNR
Q.32 What is the effect of increasing the source impedance on the noise performance of a bioamplifier?
Decreases noise
Increases noise
Has no effect
Reduces gain
Explanation - High source impedance interacts with amplifier input bias current to generate additional noise.
Correct answer is: Increases noise
Q.33 Why is the term 'low‑frequency drift' significant in ECG signal acquisition?
It causes baseline wander
It increases the amplitude of QRS
It reduces the sampling rate
It improves signal clarity
Explanation - Low‑frequency drift leads to slow changes in baseline, masking subtle ECG features.
Correct answer is: It causes baseline wander
Q.34 Which of the following is a typical output swing of a low‑power bioamplifier operating from a ±2.5 V supply?
-2.5 V to +2.5 V
-2 V to +2 V
-2.2 V to +2.2 V
-1.5 V to +1.5 V
Explanation - Many low‑power op‑amps cannot swing all the way to supply rails; typical output is ±2 V with a 5 V supply.
Correct answer is: -2 V to +2 V
Q.35 In an instrumentation amplifier, what role does resistor R3 play?
Sets the gain
Sets the input bias current
Sets the offset voltage
Provides the output impedance
Explanation - R3 is the resistor across which the differential output voltage develops; its value determines the overall gain.
Correct answer is: Sets the gain
Q.36 Which type of filter is most suitable for suppressing high‑frequency muscle artifacts in EMG signals?
Low‑pass filter at 10 Hz
High‑pass filter at 20 Hz
Band‑pass filter 20–500 Hz
Notch filter at 60 Hz
Explanation - EMG signals occupy 20–500 Hz; a band‑pass filter retains this band while removing DC and high‑frequency noise.
Correct answer is: Band‑pass filter 20–500 Hz
Q.37 Which parameter is directly affected by the thermal noise in the source resistance?
Gain
Offset voltage
Noise voltage
Bandwidth
Explanation - Thermal (Johnson) noise in the source resistance adds to the input noise voltage of the amplifier.
Correct answer is: Noise voltage
Q.38 The term 'slew rate' refers to:
Maximum output voltage swing
Maximum rate of change of the output voltage
Maximum input voltage
Maximum current supplied to the output
Explanation - Slew rate limits how quickly an amplifier can respond to rapid input changes; it matters for high‑frequency signals.
Correct answer is: Maximum rate of change of the output voltage
Q.39 Which of the following best describes the function of a 'differential probe' in biomedical instrumentation?
To increase the output voltage
To convert AC to DC
To measure the difference between two points while rejecting common‑mode noise
To provide power to the amplifier
Explanation - Differential probes isolate the measurement from ground and reduce interference.
Correct answer is: To measure the difference between two points while rejecting common‑mode noise
Q.40 Why is a 'guard' electrode often driven at the same potential as the input of an instrumentation amplifier?
To increase the input impedance
To minimize leakage currents into the input
To provide a reference voltage
To improve the bandwidth
Explanation - A guard driven at the input potential ensures that leakage currents do not flow into the amplifier, reducing offset errors.
Correct answer is: To minimize leakage currents into the input
Q.41 Which of the following is NOT a typical feature of a low‑power bioamplifier?
Ultra‑low quiescent current
High input impedance
High offset voltage
Low noise figure
Explanation - Low‑power amplifiers aim for low offset voltage to avoid baseline drift in biopotential signals.
Correct answer is: High offset voltage
Q.42 In ECG acquisition, what does the term 'baseline wander' refer to?
Rapid fluctuations in the signal
Slow changes in the DC offset
High‑frequency interference
A sudden spike in the waveform
Explanation - Baseline wander is a low‑frequency drift that shifts the average signal level over time.
Correct answer is: Slow changes in the DC offset
Q.43 What is the purpose of a 'dummy' electrode in a biopotential measurement system?
To provide a reference voltage
To measure the impedance of the skin
To mimic the input impedance of real electrodes
To serve as a ground connection
Explanation - Dummy electrodes are used during testing to emulate the characteristics of actual electrodes without contacting the body.
Correct answer is: To mimic the input impedance of real electrodes
Q.44 Which parameter indicates how well an amplifier rejects common‑mode signals?
Input impedance
CMRR
SNR
Bandwidth
Explanation - Common‑mode rejection ratio (CMRR) quantifies the ability to reject signals present on both inputs.
Correct answer is: CMRR
Q.45 The 'gain‑bandwidth product' of an op‑amp is:
The product of the amplifier's DC gain and the bandwidth where the gain is 1
The product of the amplifier's DC gain and its bandwidth at -3 dB
The sum of the gain and bandwidth
The ratio of gain to bandwidth
Explanation - Gain‑bandwidth product (GBW) is a constant for many op‑amps, indicating the trade‑off between gain and bandwidth.
Correct answer is: The product of the amplifier's DC gain and its bandwidth at -3 dB
Q.46 Which of the following best describes the function of an 'electrode pre‑amp'?
To provide power to the electrodes
To amplify the biopotential before digitization
To filter high‑frequency noise
To convert analog signals to digital
Explanation - An electrode pre‑amp increases the signal level from the electrode to a level suitable for ADC conversion.
Correct answer is: To amplify the biopotential before digitization
Q.47 Why is the term 'input common‑mode voltage range' important in biomedical instrumentation?
It limits the maximum output voltage
It determines the maximum allowable input voltage without distortion
It defines the bandwidth
It sets the minimum power requirement
Explanation - The input common‑mode voltage range specifies the voltages over which the amplifier operates linearly; exceeding it causes output clipping.
Correct answer is: It determines the maximum allowable input voltage without distortion
Q.48 Which of the following is a typical source of 1/f noise in op‑amps?
Thermal agitation in resistors
Random switching noise in MOS transistors
Shot noise in bipolar junction transistors
Magnetic interference
Explanation - 1/f noise (flicker noise) arises mainly from traps in MOS transistor channels.
Correct answer is: Random switching noise in MOS transistors
Q.49 In an instrumentation amplifier, the resistors R1 and R2 are typically equal to:
R3
R3/2
R3/4
2×R3
Explanation - In a common 3‑op‑amp design, R1 and R2 are often matched to R3 to simplify gain calculation.
Correct answer is: R3
Q.50 What is the main function of a 'differential amplifier' in a biomedical instrument?
To convert AC signals to DC
To amplify the voltage difference between two inputs
To provide power to the amplifier
To reduce the input impedance
Explanation - Differential amplifiers amplify the difference between two input signals while rejecting common‑mode components.
Correct answer is: To amplify the voltage difference between two inputs
Q.51 Which of the following is a key design consideration for the high‑frequency end of a biopotential amplifier?
Large input bias current
High input capacitance
High slew rate and low phase shift
Large output impedance
Explanation - Fast changes in the biopotential signal require an amplifier that can respond quickly without distortion.
Correct answer is: High slew rate and low phase shift
Q.52 What does the term 'noise figure' represent in an amplifier?
The ratio of output to input noise power
The amount of noise added by the amplifier per unit bandwidth
The maximum output voltage swing
The total harmonic distortion
Explanation - Noise figure quantifies how much an amplifier degrades the signal‑to‑noise ratio relative to an ideal device.
Correct answer is: The ratio of output to input noise power
Q.53 In a typical ECG front‑end, the sampling rate of the ADC should be at least how many times the maximum frequency of interest (Nyquist criterion)?
Equal to the maximum frequency
Half of the maximum frequency
Twice the maximum frequency
Four times the maximum frequency
Explanation - The Nyquist criterion requires a sampling rate of at least twice the highest frequency component to avoid aliasing.
Correct answer is: Twice the maximum frequency
Q.54 Which parameter of a resistor affects the thermal noise generated in a bioamplifier?
Resistance value
Tolerance
Color code
Power rating
Explanation - Thermal noise voltage is proportional to the square root of resistance (Vn = √(4kTRΔf)).
Correct answer is: Resistance value
Q.55 Which of the following is a typical output voltage range for a low‑noise, low‑power op‑amp powered from ±2.5 V?
-2.5 V to +2.5 V
-2 V to +2 V
-1.5 V to +1.5 V
-3 V to +3 V
Explanation - Most op‑amps cannot swing to the rails; typical output is ±2 V when powered by ±2.5 V.
Correct answer is: -2 V to +2 V
Q.56 The function of a 'buffer' (voltage follower) in a signal chain is to:
Amplify the signal
Provide high input impedance and low output impedance
Increase the bandwidth
Reduce noise
Explanation - A buffer isolates the signal source from the rest of the circuit, preventing loading and signal distortion.
Correct answer is: Provide high input impedance and low output impedance
Q.57 What is the typical maximum common‑mode voltage range for a bioamplifier intended for ECG measurement?
±5 V
±3 V
±1 V
±10 V
Explanation - ECG signals are small (mV range); most amplifiers allow a ±3 V common‑mode range to accommodate body potentials.
Correct answer is: ±3 V
Q.58 Which of the following is the most significant source of offset voltage in a biopotential measurement chain?
Power‑line interference
Input bias current on high source impedance
Thermal noise in the input resistor
Supply voltage ripple
Explanation - High source impedance interacts with input bias current, creating a voltage drop that appears as offset.
Correct answer is: Input bias current on high source impedance
Q.59 In a 3‑op‑amp instrumentation amplifier, what is the approximate output impedance?
Micro‑ohms
Ohms
Kilo‑ohms
Mega‑ohms
Explanation - Instrumentation amplifiers have very low output impedance, often in the micro‑ohm range, allowing them to drive subsequent stages easily.
Correct answer is: Micro‑ohms
Q.60 Which of the following is a common design approach to reduce the power consumption of a bioamplifier?
Use high supply voltage
Select op‑amps with low quiescent current
Increase input bias current
Add more gain stages
Explanation - Low quiescent current reduces the overall power consumption, essential for wearable medical devices.
Correct answer is: Select op‑amps with low quiescent current
Q.61 The noise performance of an amplifier is often quoted in units of:
Decibels (dB)
Volts per root hertz (V/√Hz)
Amperes (A)
Ohms (Ω)
Explanation - Input noise density is expressed as V/√Hz, indicating the noise power spectral density.
Correct answer is: Volts per root hertz (V/√Hz)
Q.62 Which of the following best describes 'electrochemical noise' in a biopotential measurement?
Noise generated by the amplifier's internal transistors
Noise caused by the skin–electrode interface
Thermal noise in resistors
Noise from power supply ripple
Explanation - Electrochemical noise arises from ion movement at the electrode–skin contact, producing low‑frequency drift.
Correct answer is: Noise caused by the skin–electrode interface
Q.63 In a typical ECG front‑end, the first stage gain is often set to:
1–2×
5–10×
10–100×
200–500×
Explanation - The raw ECG signal (~1 mV) needs moderate amplification before ADC digitization.
Correct answer is: 10–100×
Q.64 What is the purpose of a 'low‑pass filter' in a bioamplifier circuit?
To block high‑frequency noise
To block low‑frequency drift
To increase the gain
To shift the signal frequency
Explanation - Low‑pass filters suppress frequencies above the desired bandwidth, protecting the signal from high‑frequency interference.
Correct answer is: To block high‑frequency noise
Q.65 Which of the following best explains 'input offset current' in an op‑amp?
The difference between the input bias currents at the two input terminals
The current required to bias the input stage
The total input bias current
The current through the output load
Explanation - Input offset current is the mismatch between the two input bias currents, causing offset voltage in high‑impedance circuits.
Correct answer is: The difference between the input bias currents at the two input terminals
Q.66 Why are differential amplifiers preferred over single‑ended amplifiers for biopotential acquisition?
They offer higher bandwidth
They have higher input impedance
They provide common‑mode rejection
They are cheaper
Explanation - Biopotential signals are often buried in common‑mode noise; differential amplifiers reject this noise, improving measurement quality.
Correct answer is: They provide common‑mode rejection
Q.67 Which component is used to provide a virtual ground reference in a single‑supply bioamplifier?
Voltage follower
Rail‑to‑rail op‑amp
Half‑voltage divider
Operational amplifier
Explanation - A half‑voltage divider creates a virtual ground at Vcc/2, allowing the amplifier to swing symmetrically around zero.
Correct answer is: Half‑voltage divider
Q.68 In a bioamplifier, what is the typical effect of increasing the input bias voltage of an op‑amp?
Lower noise figure
Higher offset voltage
Higher power consumption
Lower bandwidth
Explanation - Higher input bias current leads to a larger voltage drop across input resistors, increasing offset voltage.
Correct answer is: Higher offset voltage
Q.69 Which of the following best describes the 'bandwidth' of an amplifier?
The range of output voltages
The frequency range where the amplifier maintains its specified gain
The maximum current it can supply
The maximum input voltage it can handle
Explanation - Bandwidth is defined as the frequency interval over which the amplifier's gain stays within a specified limit (usually 3 dB of the mid‑band gain).
Correct answer is: The frequency range where the amplifier maintains its specified gain
Q.70 Which of the following is a key advantage of using a 'single‑supply' op‑amp in biomedical instrumentation?
Higher input voltage range
Simpler power supply design
Lower noise figure
Higher common‑mode rejection
Explanation - Single‑supply op‑amps can be powered from a single battery or supply, simplifying the circuit and reducing cost.
Correct answer is: Simpler power supply design
Q.71 In a high‑gain instrumentation amplifier, which resistor primarily determines the DC offset voltage at the output?
R1
R2
R3
All of the above equally
Explanation - Any mismatch among the three resistors can introduce DC offset; precision matching is essential for low offset.
Correct answer is: All of the above equally
Q.72 Which of the following is an example of a 'passive' filter component used in bioamplifiers?
Operational amplifier
Resistor-capacitor (RC) network
Transimpedance amplifier
Differential amplifier
Explanation - Passive filters use only passive components like resistors and capacitors to shape the frequency response.
Correct answer is: Resistor-capacitor (RC) network
Q.73 Which of the following is NOT a typical application of a bioamplifier?
ECG
EMG
EEG
X‑ray imaging
Explanation - X‑ray imaging relies on photon detection, not on amplifying biological electrical signals.
Correct answer is: X‑ray imaging
Q.74 What does the term 'saturation' mean in the context of an op‑amp?
Maximum input voltage before distortion
Maximum output voltage swing
Minimum output voltage swing
Maximum input frequency
Explanation - Saturation occurs when the output reaches the supply rails and can no longer increase or decrease proportionally to the input.
Correct answer is: Maximum output voltage swing
Q.75 Which of the following is a key factor influencing the choice of the resistor value R3 in an instrumentation amplifier?
Desired gain
Input offset voltage
Output bandwidth
Input bias current
Explanation - The gain of a 3‑op‑amp instrumentation amplifier is primarily set by the ratio of R3 to R2.
Correct answer is: Desired gain
Q.76 What is the purpose of a 'common‑mode feedback' loop in an instrumentation amplifier?
To adjust the gain
To increase the bandwidth
To improve common‑mode rejection
To reduce offset voltage
Explanation - Common‑mode feedback stabilizes the CMRR by compensating for variations in supply voltage and temperature.
Correct answer is: To improve common‑mode rejection
Q.77 Which of the following is the most common source of 'thermal noise' in a bioamplifier?
Input bias current
Resistors in the circuit
Capacitors
Inductors
Explanation - Thermal (Johnson) noise arises from the random motion of charge carriers in resistive elements.
Correct answer is: Resistors in the circuit
Q.78 In an ECG system, why is a 0.05 Hz high‑pass filter commonly used?
To eliminate DC offset
To remove high‑frequency muscle noise
To prevent baseline wander
To increase the QRS amplitude
Explanation - The high‑pass filter cuts off very low frequencies, preventing slow baseline drift from corrupting the ECG waveform.
Correct answer is: To prevent baseline wander
Q.79 Which of the following is a typical 'gain' value for the second stage of a bioamplifier that performs band‑pass filtering?
1–2×
5–10×
20–50×
200–500×
Explanation - Second stage amplifiers often provide additional gain while shaping the bandwidth for the desired signal range.
Correct answer is: 20–50×
Q.80 What is the primary function of a 'transimpedance amplifier' in biopotential measurements?
To convert voltage to current
To convert current to voltage
To amplify differential voltage
To block DC offset
Explanation - Transimpedance amplifiers are used when the source provides a current, such as photodiodes or certain sensor outputs.
Correct answer is: To convert current to voltage
Q.81 Which of the following noise sources is most likely to dominate in an EMG signal acquisition circuit?
1/f noise
Johnson noise
Shot noise
Electrochemical noise
Explanation - EMG signals are low‑frequency and sensitive to flicker noise present in many op‑amps.
Correct answer is: 1/f noise
Q.82 The 'input impedance' of a bioamplifier should be:
Lower than the source impedance
Equal to the source impedance
Higher than the source impedance
Irrelevant
Explanation - High input impedance ensures minimal loading of the biopotential source, preserving signal fidelity.
Correct answer is: Higher than the source impedance
Q.83 In an instrumentation amplifier, if R2 is increased while keeping R1 and R3 constant, the gain will:
Increase
Decrease
Remain the same
Become negative
Explanation - Gain ≈ 1 + (2R2/R3); increasing R2 raises the gain proportionally.
Correct answer is: Increase
Q.84 What is the typical 'input noise density' of a low‑noise op‑amp used for ECG front‑ends?
10 mV/√Hz
10 µV/√Hz
10 nV/√Hz
10 pV/√Hz
Explanation - Low‑noise op‑amps for biopotentials often specify noise densities around 10 nV/√Hz or lower.
Correct answer is: 10 nV/√Hz
Q.85 Which of the following is a common technique to reduce offset voltage in a bioamplifier?
Use a high‑gain amplifier
Employ precision matched resistors
Add more input stages
Increase supply voltage
Explanation - Accurate resistor matching minimizes offset errors in differential and instrumentation amplifiers.
Correct answer is: Employ precision matched resistors
Q.86 In a bioamplifier, the 'low‑frequency cutoff' is typically set to:
0 Hz
0.05 Hz
5 Hz
50 Hz
Explanation - Setting the low‑frequency cutoff around 0.05 Hz prevents baseline wander while preserving the ECG waveform.
Correct answer is: 0.05 Hz
Q.87 Which parameter of an op‑amp is most critical when designing a bioamplifier for a high‑impedance source?
Slew rate
Input bias current
Output voltage swing
Bandwidth
Explanation - High source impedance makes the circuit sensitive to input bias current, which can create offset errors.
Correct answer is: Input bias current
Q.88 Which of the following is a typical application of an 'instrumentation amplifier' in medical devices?
High‑speed ADC conversion
Biopotential amplification (ECG, EMG, EEG)
Power supply regulation
Audio signal processing
Explanation - Instrumentation amplifiers are used to amplify small, low‑frequency biopotential signals with high common‑mode rejection.
Correct answer is: Biopotential amplification (ECG, EMG, EEG)
Q.89 What is the main drawback of using a high‑gain op‑amp in a low‑frequency biomedical signal chain?
Increased power consumption
Higher input bias current causing offset
Reduced bandwidth
Higher noise figure
Explanation - High‑gain amplifiers often require larger bias currents, which can increase offset when dealing with high source impedance.
Correct answer is: Higher input bias current causing offset
Q.90 In a differential measurement, the 'common‑mode signal' refers to:
Signal that appears only on one input
Signal that appears on both inputs with equal magnitude
Signal that is amplified by the amplifier
Signal that is ignored by the amplifier
Explanation - Common‑mode signals are present on both inputs equally and should be rejected by a differential or instrumentation amplifier.
Correct answer is: Signal that appears on both inputs with equal magnitude
Q.91 Which of the following techniques can be used to mitigate motion artifacts in an ECG circuit?
Use a higher sampling rate
Add a high‑pass filter at 0.5 Hz
Add a low‑pass filter at 200 Hz
Increase the amplifier gain
Explanation - A high‑pass filter removes low‑frequency motion artifacts while preserving the ECG waveform.
Correct answer is: Add a high‑pass filter at 0.5 Hz
Q.92 Which of the following best describes the function of a 'reference electrode' in an ECG system?
To provide a ground connection
To supply power to the amplifier
To create a common reference potential for the differential measurement
To shield the electrodes from EMI
Explanation - The reference electrode provides a stable potential against which the active electrodes are measured.
Correct answer is: To create a common reference potential for the differential measurement
Q.93 What is the typical maximum input voltage that an instrumentation amplifier can tolerate without distortion?
1 V
5 V
10 V
50 V
Explanation - Most instrumentation amplifiers are rated for input voltages up to a few volts; exceeding this can lead to clipping.
Correct answer is: 5 V
Q.94 Which of the following is a common method to reduce the impact of supply‑noise on a biopotential amplifier?
Use a linear regulator
Use a switching regulator
Increase the supply voltage
Add more gain stages
Explanation - Linear regulators provide clean, low‑noise supply voltages, essential for sensitive biopotential measurements.
Correct answer is: Use a linear regulator
Q.95 In a bioamplifier, the 'input noise voltage' of an op‑amp is often specified as:
V/√Hz
µV
pA
Hz
Explanation - Noise voltage density indicates the noise contribution per square root hertz of bandwidth.
Correct answer is: V/√Hz
Q.96 Which of the following best explains the term 'shunt‑capacitor' in a bioamplifier design?
A capacitor connected across the input to reduce noise
A capacitor used to block DC from the signal
A capacitor used to provide a reference voltage
A capacitor used in the output stage
Explanation - Shunt capacitors are used to filter high‑frequency noise or to set the input impedance with the bias resistor.
Correct answer is: A capacitor connected across the input to reduce noise
Q.97 What is the benefit of using a 'dual‑rail' supply for an op‑amp in biomedical instrumentation?
Simplifies PCB layout
Allows the amplifier to output both positive and negative voltages
Increases noise immunity
Reduces power consumption
Explanation - Dual‑rail supplies (+V and –V) enable the amplifier to swing around zero, which is often required for differential biopotential signals.
Correct answer is: Allows the amplifier to output both positive and negative voltages
Q.98 Which of the following is a typical 'gain' for an ECG front‑end first stage?
1–5×
10–100×
200–500×
1000×
Explanation - An ECG signal is typically ~1 mV; a gain of 10–100× brings it to a measurable voltage range for ADC conversion.
Correct answer is: 10–100×
Q.99 Which of the following is NOT a typical parameter of a bioamplifier design?
Gain
Bandwidth
Input offset voltage
Output capacitance
Explanation - While output capacitance can affect performance, it is not a standard design specification for biopotential amplifiers.
Correct answer is: Output capacitance
Q.100 What is the primary role of the 'ground reference' electrode in a bioamplifier system?
To provide the lowest potential point for the measurement
To supply power to the amplifier
To act as a shield against EMI
To set the common‑mode voltage
Explanation - The ground electrode is typically at or near earth potential, serving as the return path for the measurement current.
Correct answer is: To provide the lowest potential point for the measurement
Q.101 Which of the following is a typical method to reduce the effect of electrode impedance mismatch in a differential amplifier?
Use a high‑gain amplifier
Match the electrode impedances carefully
Add a low‑pass filter
Use a single‑supply op‑amp
Explanation - Impedance mismatches reduce CMRR, causing more common‑mode noise to appear at the output.
Correct answer is: Match the electrode impedances carefully
Q.102 Which of the following components is used to implement a low‑frequency high‑pass filter for biopotential signals?
Resistor and inductor
Resistor and capacitor
Inductor and capacitor
Capacitor and inductor
Explanation - A simple RC high‑pass filter uses a resistor and capacitor to set the cutoff frequency for low‑frequency signals.
Correct answer is: Resistor and capacitor
Q.103 Which of the following best describes the purpose of a 'low‑swing' op‑amp in a biomedical application?
To handle high input voltages
To provide a large output swing
To operate from a low supply voltage
To increase bandwidth
Explanation - Low‑swing op‑amps can operate from small supply rails (e.g., 3 V), useful in portable biomedical devices.
Correct answer is: To operate from a low supply voltage
Q.104 Which of the following is a key advantage of using a differential amplifier over a single‑ended amplifier in a biopotential measurement?
Lower cost
Higher gain
Common‑mode noise rejection
Higher bandwidth
Explanation - Differential amplifiers reject signals common to both inputs, reducing noise from the environment.
Correct answer is: Common‑mode noise rejection
Q.105 Which parameter of a low‑noise amplifier is most important when measuring EMG signals?
Slew rate
Input noise density
Input bias current
Output voltage swing
Explanation - EMG signals are weak and frequency‑limited; low input noise density ensures the signal is not lost in amplifier noise.
Correct answer is: Input noise density
Q.106 What is the typical input impedance of an instrumentation amplifier used in medical signal acquisition?
10 kΩ
100 kΩ
1 MΩ
>10 MΩ
Explanation - Instrumentation amplifiers are designed with input impedances in the GΩ range to match the high impedance of biopotential sources.
Correct answer is: >10 MΩ
Q.107 In a bioamplifier, what is the effect of a large input resistor value?
Reduced noise
Increased noise due to thermal noise
Decreased power consumption
Improved bandwidth
Explanation - Higher resistance increases thermal noise (√(4kTR)), potentially degrading signal quality.
Correct answer is: Increased noise due to thermal noise
Q.108 Which of the following is a common type of electrode used for EEG recordings?
Ag/AgCl disc
Glass electrode
Piezoelectric sensor
Photodiode
Explanation - Silver‑chloride (Ag/AgCl) electrodes are standard for EEG due to their stable electrochemical properties.
Correct answer is: Ag/AgCl disc
Q.109 Which of the following statements about the CMRR of an instrumentation amplifier is correct?
It is independent of resistor tolerance
It decreases with temperature changes
It is typically higher than that of a simple differential amplifier
It is always less than 100 dB
Explanation - Instrumentation amplifiers incorporate internal resistor networks that provide CMRR values often exceeding 80 dB.
Correct answer is: It is typically higher than that of a simple differential amplifier
Q.110 Which of the following is a common noise source in an ECG system?
Thermal noise in resistors
Ambient magnetic fields
Power‑line interference (50/60 Hz)
All of the above
Explanation - ECG signals are susceptible to multiple noise sources, including thermal, magnetic, and power‑line interference.
Correct answer is: All of the above
Q.111 What is the purpose of the 'bias voltage' applied to the reference electrode in an ECG system?
To provide a stable reference potential
To supply power to the amplifier
To shield the electrodes from EMI
To increase the signal amplitude
Explanation - Bias voltage stabilizes the reference electrode potential, ensuring consistent differential measurement.
Correct answer is: To provide a stable reference potential
Q.112 Which of the following is a key feature of a 'single‑supply' bioamplifier design?
It can handle only positive signals
It requires a virtual ground to measure AC signals
It cannot use an instrumentation amplifier
It has a higher input impedance
Explanation - Single‑supply designs often create a virtual ground at Vcc/2 to allow AC signals to oscillate around zero.
Correct answer is: It requires a virtual ground to measure AC signals
Q.113 In an ECG front‑end, why is the 'gain‑bandwidth product' of the op‑amp important?
To ensure enough bandwidth for the desired gain
To reduce noise
To increase the input impedance
To lower the power consumption
Explanation - The GBW determines the maximum achievable gain for a given bandwidth; a high GBW allows both high gain and adequate bandwidth.
Correct answer is: To ensure enough bandwidth for the desired gain
Q.114 Which of the following components is typically used to implement a 'high‑pass filter' at 0.5 Hz in a bioamplifier?
Resistor and capacitor
Inductor and resistor
Capacitor and inductor
Resistor and diode
Explanation - A high‑pass filter is formed with a resistor and capacitor in series, with the capacitor shunting the low frequencies.
Correct answer is: Resistor and capacitor
Q.115 Which of the following is an example of a 'passive filter' used in bioamplifiers?
Operational amplifier
Voltage follower
Resistor‑capacitor network
Transimpedance amplifier
Explanation - Passive filters rely only on passive elements like resistors and capacitors, with no active amplification.
Correct answer is: Resistor‑capacitor network
Q.116 What is the main reason for using a 'differential amplifier' in a bioamplifier circuit?
To provide a single‑ended output
To increase the input impedance
To reject common‑mode noise
To reduce the supply voltage
Explanation - Differential amplifiers amplify only the voltage difference between inputs, suppressing common‑mode interference.
Correct answer is: To reject common‑mode noise
Q.117 Which of the following is the most common type of noise present in biopotential measurements?
Thermal noise
Shot noise
Electrochemical noise
All of the above
Explanation - Biopotential signals are affected by multiple noise sources, each requiring different mitigation strategies.
Correct answer is: All of the above
Q.118 Which parameter of an instrumentation amplifier determines its ability to reject common‑mode signals?
Input impedance
CMRR
Gain bandwidth product
Offset voltage
Explanation - Common‑mode rejection ratio (CMRR) quantifies how well an amplifier can cancel signals common to both inputs.
Correct answer is: CMRR
Q.119 In a typical ECG front‑end, the output of the amplifier is typically connected to:
A digital signal processor (DSP)
An analog-to-digital converter (ADC)
A voltage regulator
A power supply unit
Explanation - The amplified ECG signal is digitized by an ADC for further digital processing and storage.
Correct answer is: An analog-to-digital converter (ADC)
Q.120 Which of the following is a common method to reduce the impact of electrode impedance in a biopotential system?
Use high‑gain amplifiers
Add a low‑pass filter
Use a high‑impedance front‑end amplifier
Increase the supply voltage
Explanation - High‑impedance amplifiers minimize loading effects from the electrode–skin impedance.
Correct answer is: Use a high‑impedance front‑end amplifier
Q.121 Which of the following is a key factor influencing the noise performance of a biopotential amplifier?
Input bias current
Input noise density
Gain bandwidth product
Output voltage swing
Explanation - Input noise density directly determines the amount of noise added per hertz of bandwidth.
Correct answer is: Input noise density
Q.122 What does a 'saturation voltage' refer to in an op‑amp?
The maximum input voltage before distortion
The maximum output voltage swing
The maximum frequency response
The minimum input impedance
Explanation - Saturation occurs when the output reaches the supply rails and cannot follow the input signal.
Correct answer is: The maximum output voltage swing
Q.123 Which of the following is a common type of electrode for EMG measurements?
Ag/AgCl disc
Glass electrode
Piezoelectric sensor
Metal strip electrode
Explanation - Metal strip electrodes are commonly used for surface EMG due to their flexibility and good contact with the skin.
Correct answer is: Metal strip electrode
Q.124 Why is it important to match the resistors used in an instrumentation amplifier?
To minimize offset voltage
To increase gain
To reduce input bias current
To reduce power consumption
Explanation - Resistor mismatches cause offset errors; precise matching keeps offsets low.
Correct answer is: To minimize offset voltage
Q.125 What is the typical 'gain' range of an instrumentation amplifier used for EEG signals?
1–10×
10–100×
100–1000×
1000–10,000×
Explanation - EEG signals are in the microvolt range, requiring high gain (100–1000×) to be digitized accurately.
Correct answer is: 100–1000×
Q.126 Which of the following is an advantage of using a 'dual‑rail' supply for an op‑amp in a biomedical device?
Simplifies PCB design
Reduces supply noise
Enables output swing around zero
Decreases power consumption
Explanation - Dual‑rail supplies (+V and –V) allow the amplifier to output both positive and negative voltages, essential for differential signals.
Correct answer is: Enables output swing around zero
Q.127 In a biopotential measurement, the 'common‑mode input voltage' is:
The difference between the two input voltages
The voltage common to both inputs
The output voltage of the amplifier
The voltage at the reference electrode
Explanation - Common‑mode voltage is the same voltage present on both inputs, which should be rejected by the amplifier.
Correct answer is: The voltage common to both inputs
Q.128 Which of the following best describes the role of an 'electrode guard' in a bioamplifier?
To provide a reference voltage
To block DC offset
To reduce leakage currents into the input
To shield the amplifier from EMI
Explanation - Guard electrodes drive at the same potential as the input, minimizing leakage currents that can cause offset errors.
Correct answer is: To reduce leakage currents into the input
Q.129 Which of the following is a typical characteristic of a 'low‑power' op‑amp suitable for wearable medical devices?
High input bias current
High noise figure
Low quiescent current
Large supply voltage range
Explanation - Low quiescent current (< µA) allows wearable devices to run on small batteries for extended periods.
Correct answer is: Low quiescent current
Q.130 The 'bandwidth' of a bioamplifier is typically set to:
0 Hz to 200 Hz for ECG
20 Hz to 500 Hz for EMG
0.05 Hz to 150 Hz for ECG
All of the above
Explanation - Different biopotentials have distinct frequency ranges; the amplifier bandwidth is chosen accordingly.
Correct answer is: All of the above
Q.131 Which of the following is a common source of noise in a low‑impedance biomedical circuit?
Electrochemical noise
Thermal noise
Shot noise
All of the above
Explanation - Even in low‑impedance circuits, multiple noise sources can affect the signal and must be considered.
Correct answer is: All of the above
Q.132 What is the purpose of using a 'voltage follower' in a biopotential measurement chain?
To increase the input impedance
To provide high gain
To block DC offset
To act as a buffer between stages
Explanation - A voltage follower presents a high input impedance and low output impedance, isolating stages and preventing loading.
Correct answer is: To act as a buffer between stages
Q.133 In a bioamplifier, which of the following is a common technique to mitigate the effect of power‑line interference?
Use a low‑swing op‑amp
Add a 60‑Hz notch filter
Increase the input impedance
Add a high‑pass filter at 0.5 Hz
Explanation - A notch filter at 60 Hz effectively removes line interference without affecting the desired signal band.
Correct answer is: Add a 60‑Hz notch filter
Q.134 Which of the following best describes the 'input offset voltage' of an op‑amp?
The maximum output voltage swing
The voltage difference that produces zero output
The minimum input voltage
The noise level at the input
Explanation - Input offset voltage is the differential voltage required at the inputs to make the output zero.
Correct answer is: The voltage difference that produces zero output
Q.135 What does the 'saturation voltage' of an op‑amp represent?
The maximum input voltage before distortion
The maximum output voltage swing
The maximum supply voltage
The input bias current
Explanation - Saturation occurs when the amplifier's output reaches the supply rails and cannot follow the input.
Correct answer is: The maximum output voltage swing
Q.136 In a biomedical instrumentation circuit, which of the following is a typical requirement for the input bias current of an op‑amp?
High (≥ µA)
Moderate (≈ nA)
Very low (≤ pA)
Zero
Explanation - Very low input bias currents minimize offset errors when dealing with high‑impedance biopotential sources.
Correct answer is: Very low (≤ pA)
Q.137 Which of the following is a typical application of a 'differential amplifier' in medical instrumentation?
High‑frequency audio processing
ECG signal amplification
Power supply regulation
Temperature measurement
Explanation - Differential amplifiers are commonly used to amplify the small differential ECG signal while rejecting common‑mode noise.
Correct answer is: ECG signal amplification
Q.138 The 'input bias current' of an op‑amp can cause a voltage drop across which of the following?
Output resistor
Input resistor
Power supply
Ground reference
Explanation - Bias current flowing through the input resistor creates a voltage drop, contributing to offset error.
Correct answer is: Input resistor
Q.139 Which of the following is a typical feature of a 'low‑noise' op‑amp used in a bioamplifier?
High input bias current
High input noise density
Low input noise density
Low common‑mode rejection ratio
Explanation - Low input noise density ensures the amplifier adds minimal noise to the biopotential signal.
Correct answer is: Low input noise density
Q.140 What does a 'common‑mode feedback' loop in an instrumentation amplifier do?
Adjusts the gain
Stabilizes the common‑mode rejection ratio
Reduces offset voltage
Increases bandwidth
Explanation - Common‑mode feedback compensates for changes in supply voltage and temperature, improving CMRR.
Correct answer is: Stabilizes the common‑mode rejection ratio
Q.141 Which of the following is a typical input impedance for a biopotential amplifier front‑end?
1 kΩ
10 kΩ
1 MΩ
10 MΩ
Explanation - High input impedance (10 MΩ or greater) minimizes loading on the biopotential source.
Correct answer is: 10 MΩ
Q.142 In a bioamplifier, why is a 'high‑gain' stage often followed by a 'low‑pass filter'?
To increase the input impedance
To protect the amplifier from saturation due to high‑frequency noise
To boost the signal amplitude further
To improve the bandwidth of the signal
Explanation - A low‑pass filter limits the bandwidth, preventing high‑frequency noise from being amplified excessively.
Correct answer is: To protect the amplifier from saturation due to high‑frequency noise
Q.143 Which of the following best explains the concept of 'thermal noise' in a resistor?
Noise generated by ion movement
Noise from the supply voltage ripple
Noise from random motion of charge carriers
Noise due to temperature changes only
Explanation - Thermal (Johnson) noise arises from the random movement of electrons in a resistor.
Correct answer is: Noise from random motion of charge carriers
Q.144 Which of the following is a typical reason for selecting a 'rail‑to‑rail' op‑amp in a medical device?
To handle high input voltages
To provide full‑rail output swing
To reduce input offset voltage
To increase gain bandwidth product
Explanation - Rail‑to‑rail op‑amps can drive outputs close to the supply rails, which is useful in low‑voltage medical devices.
Correct answer is: To provide full‑rail output swing