The pole-zero diagram of a causal system shows poles at z = 0.3 and z = 0.7, with a zero at z = 0. The system is:

The correct answer is B: High-pass filter. Zero at z=0 (DC) causes attenuation at low frequencies. Poles near z=1 allow high frequencies to pass, characteristic of a high-pass filter.

A system with H(z) = (z-0.5)/(z-0.8) has:

The correct answer is A: One zero at z=0.5 and one pole at z=0.8. Numerator gives zeros: z=0.5. Denominator gives poles: z=0.8

Which type of feedback is applied in a non-inverting amplifier configuration?

The correct answer is B: Negative feedback. Non-inverting amplifier uses negative feedback from output to inverting input, which reduces gain but improves linearity, bandwidth, and input impedance.

What is the Boolean expression for a 2-input NAND gate?

The correct answer is B: Y = (A.B)'. NAND gate is the complement of AND, so Y = (A.B)' where . represents AND operation.

In a Push-Pull (Class B) amplifier, what is the primary disadvantage that Class AB configuration addresses?

The correct answer is A: Crossover distortion. Class B exhibits crossover distortion where both transistors are off near the zero-crossing point. Class AB adds small quiescent bias to keep transistors in active region, eliminating this distortion.

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Electronics (ECE)

Analog/digital electronics, communication

187 Q 4 Topics Take Mock Test

Difficulty: All Easy Medium Hard 171–180 of 187

Topics in Electronics (ECE)

All Electronic Devices 100 Digital Electronics 100 Analog Circuits 100 Signals & Systems 100

Q.171 Medium Electronic Devices

Which statement correctly describes the Early effect in BJTs?

A Base current increases without input signal change

B Early voltage depends on doping concentration and geometry

C It causes constant gain independent of VCE

D Collector current decreases as VCE decreases

Correct Answer: B. Early voltage depends on doping concentration and geometry

EXPLANATION

Early voltage (VA) is a parameter that depends on the base width modulation effect with collector-base reverse bias voltage.

Test

Q.172 Medium Electronic Devices

A MOSFET operating in triode (linear) region exhibits:

A VDS > VGS - VTh

B VDS < VGS - VTh

C VDS = VGS - VTh

D VDS is independent of VGS

Correct Answer: B. VDS < VGS - VTh

EXPLANATION

In triode region, the condition VDS < VGS - VTh allows the channel to conduct with resistance proportional to VDS.

Test

Q.173 Medium Electronic Devices

In a thyristor (SCR), the holding current (IH) is important because:

A It determines maximum forward current

B It is the minimum current required to maintain conduction after gate pulse is removed

C It controls the forward voltage drop

D It increases with temperature

Correct Answer: B. It is the minimum current required to maintain conduction after gate pulse is removed

EXPLANATION

Holding current IH: minimum anode current to sustain regenerative action (latching); if IA < IH, device reverts to blocking state.

Test

Q.174 Medium Electronic Devices

In a photodiode, the photocurrent is proportional to:

A Applied reverse bias voltage

B Incident light intensity and quantum efficiency

C Forward bias current

D Operating temperature

Correct Answer: B. Incident light intensity and quantum efficiency

EXPLANATION

Photodiode: Iph = η·q·Φ where η is quantum efficiency and Φ is incident photon flux; reverse bias increases depletion width for carrier collection.

Test

Q.175 Medium Electronic Devices

Channel length modulation in MOSFETs causes:

A Reduced saturation current

B Finite output impedance Rds ≈ VA/ID

C Increased threshold voltage

D Zero Early voltage effect

Correct Answer: B. Finite output impedance Rds ≈ VA/ID

EXPLANATION

CLM: as VDS increases, pinch-off point moves toward source, reducing effective channel length; output resistance Rds = VA/ID = λ⁻¹.

Test

Q.176 Medium Electronic Devices

The gain-bandwidth product (GBP) of a BJT is approximately equal to:

A Current gain × operating frequency

B Transconductance / gate capacitance

C fT (transit frequency) where hFE·fβ = constant

D Collector current / base-emitter voltage

Correct Answer: C. fT (transit frequency) where hFE·fβ = constant

EXPLANATION

GBW ≈ fT; BJT current gain drops with frequency as β·f ≈ constant, where fT is extrapolated cutoff frequency (~1GHz for silicon BJTs).

Test

Q.177 Medium Electronic Devices

In a CMOS inverter, the power dissipation is primarily due to:

A Leakage current only

B Static current during logic transitions

C Dynamic current during charging/discharging of load capacitance

D Forward bias voltage drop

Correct Answer: C. Dynamic current during charging/discharging of load capacitance

EXPLANATION

CMOS dynamic power = CV²f dominates; ideal CMOS has zero static power as pull-up and pull-down never conduct simultaneously.

Test

Q.178 Medium Electronic Devices

In a BJT operating in the active region, which relationship holds true?

A VCE < 0.2V

B VBE ≈ 0.7V and VCE > VCE(sat)

C Both VCE and VBE are zero

D VCE > VBE by more than 1V

Correct Answer: B. VBE ≈ 0.7V and VCE > VCE(sat)

EXPLANATION

Active region requires base-emitter junction forward biased (~0.7V) and collector-base reverse biased (VCE > saturation voltage).

Test

Q.179 Medium Electronic Devices

A PIN diode is primarily used in high-frequency applications because:

A It has lower capacitance than regular diodes

B The intrinsic region reduces junction capacitance and increases minority carrier lifetime

C It operates at higher forward bias voltages

D It has better thermal stability

Correct Answer: B. The intrinsic region reduces junction capacitance and increases minority carrier lifetime

EXPLANATION

PIN diodes have wide intrinsic region that reduces capacitance while increasing carrier transit time, ideal for RF switching.

Test

Q.180 Medium Electronic Devices

In a p-n junction diode, the depletion region width depends on which of the following factors?

A Applied voltage and doping concentrations

B Temperature and light intensity only

C Forward bias voltage only

D Frequency of applied signal

Correct Answer: A. Applied voltage and doping concentrations

EXPLANATION

Depletion width W = √(2εV/qNd·Na/(Nd+Na)), dependent on applied voltage and doping concentrations.

Test

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