Analog Electronics MCQs 2026

A semiconductor diode conducts heavily when

1. A reverse biased above breakdown always without limit ✓
2. B unbiased at thermal equilibrium only for heavy conduction ✓
3. C forward biased beyond knee voltage ✓
4. D connected in parallel with reverse diode only ✓

Reverse saturation current in an ideal silicon diode at room temperature is

1. A equal to forward current always ✓
2. B very small (nanoampere range) ✓
3. C in the ampere range typically ✓
4. D proportional to forward voltage squared only ✓

Zener diode is primarily used for

1. A rectification in forward region only ✓
2. B oscillation without feedback ✓
3. C current amplification like a BJT ✓
4. D voltage regulation in reverse breakdown region ✓

Peak inverse voltage (PIV) rating of a rectifier diode is

1. A maximum forward current only ✓
2. B power dissipation at room temperature only ✓
3. C junction capacitance at zero bias ✓
4. D maximum reverse voltage the diode can withstand without breakdown ✓

Half-wave rectifier output contains

1. A pure DC without any ripple ✓
2. B only one polarity of the input AC waveform ✓
3. C both polarities equally ✓
4. D only high-frequency harmonics without fundamental ✓

Full-wave bridge rectifier requires

1. A two diodes and center tap always ✓
2. B four diodes and no center-tapped transformer ✓
3. C one diode only ✓
4. D six diodes in star connection ✓

Ripple factor of a rectifier output indicates

1. A only DC average without AC content ✓
2. B reverse breakdown voltage margin ✓
3. C transistor beta value ✓
4. D amount of AC component relative to DC component ✓

LED emits light when

1. A reverse breakdown occurs without recombination ✓
2. B electrons and holes recombine at the PN junction ✓
3. C only thermal heating without injection ✓
4. D gate voltage controls channel only like MOSFET ✓

Schottky diode has lower forward voltage drop than PN junction diode because

1. A it uses only indirect bandgap silicon always ✓
2. B it has no depletion region ever ✓
3. C metal-semiconductor junction has smaller barrier height ✓
4. D it operates only in Zener breakdown ✓

Diode dynamic resistance rd is defined as

1. A slope of V-I curve at the operating point (dv/di) ✓
2. B reverse saturation current only ✓
3. C maximum forward current rating ✓
4. D thermal voltage times beta ✓

Avalanche breakdown in a diode occurs when

1. A forward bias exceeds knee slightly only ✓
2. B gate oxide ruptures in MOSFET ✓
3. C only tunneling without multiplication ✓
4. D minority carriers accelerate and create impact ionization ✓

Tunnel (Zener) breakdown dominates in heavily doped junctions at

1. A very high reverse voltage only above 100 V always ✓
2. B forward conduction region only ✓
3. C lower reverse voltages (typically below about 5 V in silicon) ✓
4. D only in germanium without silicon ✓

Varactor diode capacitance varies with

1. A reverse bias voltage ✓
2. B forward current only without voltage dependence ✓
3. C temperature only without bias ✓
4. D gate threshold in MOSFET sense ✓

Rectifier diode selection must consider

1. A only LED color wavelength ✓
2. B forward current rating, PIV and switching speed for the application ✓
3. C only op-amp slew rate ✓
4. D only flip-flop clock frequency without power ✓

In a common-emitter BJT amplifier, base current controls

1. A drain current without gate voltage ✓
2. B only emitter reverse leakage ✓
3. C large collector current via current gain β ✓
4. D op-amp offset voltage directly ✓

BJT operates in saturation when

1. A collector-base junction is reverse biased only ✓
2. B emitter is open circuit ✓
3. C gate voltage is below threshold ✓
4. D both junctions are forward biased and VCE is small ✓

Common-collector (emitter follower) configuration has

1. A low input and high output impedance ✓
2. B high input impedance and low output impedance ✓
3. C voltage gain much greater than 100 typically ✓
4. D inverted output relative to input always ✓

Audio power amplifier heat sink sizing depends on

1. A only voltage gain in dB ✓
2. B only input bias current in pA ✓
3. C only LED forward voltage ✓
4. D power dissipation and thermal resistance to ambient ✓

Emitter degeneration resistor without bypass

1. A maximizes AC gain unconditionally ✓
2. B prevents any collector current flow ✓
3. C stabilizes bias and reduces gain but improves linearity ✓
4. D replaces the need for coupling capacitor ✓

Op-amp input offset voltage causes

1. A small DC output error even with zero input signal ✓
2. B infinite bandwidth always ✓
3. C oscillation without any feedback ✓
4. D input impedance to become zero ✓

Non-inverting amplifier closed-loop gain is

1. A 1 + Rf/R1 ✓
2. B −Rf/R1 only ✓
3. C Rf/R1 without unity term ✓
4. D zero always with feedback ✓

Inverting amplifier closed-loop gain is

1. A 1 + Rf/Rin without sign inversion ✓
2. B Rf × Rin product only ✓
3. C independent of feedback resistors ✓
4. D −Rf/Rin ✓

Virtual short between inputs of op-amp in negative feedback means

1. A both inputs are physically shorted externally ✓
2. B inputs carry equal large current always ✓
3. C voltage difference between inputs is approximately zero ✓
4. D output is always saturated ✓

Ideal operational amplifier has

1. A zero gain and zero input impedance ✓
2. B infinite open-loop gain, infinite input impedance and zero output impedance ✓
3. C finite gain of unity only always ✓
4. D output impedance equal to 50 Ω always ✓

Safe operating area (SOA) of a transistor specifies

1. A only maximum power at DC only without pulse duty ✓
2. B permissible combinations of voltage and current without damage ✓
3. C only beta at one current point ✓
4. D only op-amp bandwidth ✓

FET is preferred in high-input-impedance amplifier front ends because

1. A gate draws negligible DC current ✓
2. B collector draws maximum base current ✓
3. C emitter is always forward biased heavily ✓
4. D drain current equals gate current always ✓

Darlington pair provides

1. A unity voltage gain only without current gain ✓
2. B negative input impedance always ✓
3. C oscillation without feedback guaranteed ✓
4. D very high current gain with two cascaded transistors ✓

Channel length modulation in MOSFET is analogous to

1. A Early effect in BJT ✓
2. B Zener breakdown in diodes only ✓
3. C hysteresis in Schmitt trigger only ✓
4. D sampling aliasing only ✓

MOSFET switching speed is generally faster than BJT because

1. A higher beta always ✓
2. B larger thermal mass always ✓
3. C majority carrier transport avoids stored minority charge ✓
4. D always requires higher supply voltage ✓

BJT current gain β decreases at high collector current due to

1. A only decrease in supply voltage ✓
2. B only increase in gate threshold ✓
3. C high-level injection and base spreading resistance effects ✓
4. D only diode reverse leakage ✓

Transconductance gm of a FET relates

1. A small-signal drain current change to gate-source voltage change ✓
2. B collector current to base current only ✓
3. C diode forward voltage to current only ✓
4. D output voltage to supply voltage only ✓

JFET gate input impedance is

1. A very high because gate junction is reverse biased ✓
2. B very low like forward-biased diode ✓
3. C equal to 50 Ω always ✓
4. D determined by collector load resistor only ✓

Depletion-mode MOSFET differs from enhancement mode in that it

1. A never conducts without positive VGS always ✓
2. B has no channel at manufacture ✓
3. C uses only PNP structure ✓
4. D conducts with VGS = 0 and requires negative VGS to turn off (n-channel) ✓

Enhancement-mode n-channel MOSFET conducts when

1. A VGS exceeds threshold voltage positively ✓
2. B VGS is zero without channel ever ✓
3. C VDS alone creates channel without gate ✓
4. D gate is left floating for heavy conduction ✓

Early effect in a BJT causes

1. A gate threshold to decrease only in MOSFET ✓
2. B collector current to increase slightly with collector-emitter voltage ✓
3. C diode PIV to double ✓
4. D inductor core saturation ✓

MOSFET is a

1. A voltage-controlled device via gate-source voltage ✓
2. B current-controlled device like BJT base ✓
3. C majority carrier device only in depletion mode always without exception ✓
4. D bipolar device with two PN junctions ✓

Coupling capacitor between amplifier stages blocks

1. A AC signal entirely without DC block ✓
2. B only high frequencies above 1 MHz always ✓
3. C feedback path unconditionally ✓
4. D DC bias while passing AC signal ✓

Class AB amplifier improves on Class B by

1. A eliminating all feedback ✓
2. B providing small bias so both devices conduct near crossover ✓
3. C using only single transistor ✓
4. D operating only in cutoff always ✓

Class B push-pull amplifier each transistor conducts for

1. A full 360° each simultaneously ✓
2. B approximately 180° of the cycle ✓
3. C 90° only without crossover region ✓
4. D 0° so no output ever ✓

Class A amplifier conducts

1. A only 180° of cycle ✓
2. B less than 90° only ✓
3. C only during negative half-cycle ✓
4. D for the full 360° of the input cycle ✓

Power amplifier is designed to deliver

1. A only microvolt signals to high-impedance probes ✓
2. B logic levels to CMOS gates only ✓
3. C significant power to the load efficiently ✓
4. D DC offset calibration only ✓

Voltage amplifier ideally increases

1. A current without voltage change ✓
2. B power factor of mains only ✓
3. C signal voltage with minimal loading of source ✓
4. D frequency of carrier without gain ✓

Rail-to-rail op-amp output stage allows

1. A output fixed at mid-supply only ✓
2. B input only on positive rail without negative ✓
3. C operation without power supplies ✓
4. D output swing close to both supply rails ✓

Schmitt trigger using op-amp provides

1. A pure integration without thresholds ✓
2. B zero output swing always ✓
3. C infinite CMRR without resistors ✓
4. D hysteresis to avoid chatter on noisy input signals ✓

Gain-bandwidth product of an op-amp is approximately constant for

1. A all frequencies without rolloff ✓
2. B single-pole dominant response in closed-loop designs ✓
3. C DC offset only ✓
4. D comparator hysteresis only ✓

Input bias current of op-amp is

1. A AC ripple on output only ✓
2. B slew rate in V/μs ✓
3. C closed-loop gain in dB only ✓
4. D average DC current required by the input terminals ✓

Op-amp comparator output saturates to

1. A always mid-rail without saturation ✓
2. B analog value proportional to difference in linear mode always ✓
3. C near positive or negative supply depending on input difference ✓
4. D zero without supply ✓

Differentiator op-amp circuit uses

1. A only resistors in both paths ✓
2. B inductor in feedback without capacitor ✓
3. C capacitor at the input and resistor in feedback ✓
4. D Zener diode for clipping only ✓

Integrator op-amp circuit uses

1. A inductor in input only without capacitor ✓
2. B capacitor in the feedback path ✓
3. C resistor-only feedback for integration ✓
4. D diode bridge in feedback ✓

Unity-gain buffer (voltage follower) uses

1. A positive feedback only ✓
2. B 100% negative feedback from output to inverting input ✓
3. C no feedback connection ✓
4. D open-loop operation only ✓

Common-mode rejection ratio (CMRR) measures

1. A differential gain only without common signal ✓
2. B output short-circuit current only ✓
3. C supply voltage ripple only ✓
4. D ability to reject equal signals applied to both inputs ✓

Freewheeling diode across an inductive load prevents

1. A large voltage spikes when switching current off ✓
2. B forward voltage drop from existing ✓
3. C oscillator startup without feedback ✓
4. D op-amp input offset drift ✓

Slew rate of an op-amp limits

1. A maximum rate of change of output voltage ✓
2. B DC gain only ✓
3. C input bias current only ✓
4. D common-mode rejection at DC only ✓

Bypass capacitor across emitter resistor in CE stage

1. A increases AC gain by shorting emitter resistance at signal frequency ✓
2. B reduces AC gain to zero always ✓
3. C blocks AC to the base ✓
4. D replaces collector load ✓

Transformer coupling in amplifiers provides

1. A infinite bandwidth without leakage inductance ✓
2. B elimination of all AC coupling ✓
3. C DC isolation and impedance matching between stages ✓
4. D direct connection of base to collector ✓

Total harmonic distortion (THD) measures

1. A only DC offset magnitude ✓
2. B only noise floor without harmonics ✓
3. C harmonic content relative to fundamental in output ✓
4. D slew rate limit only ✓

Differential amplifier rejects

1. A differential signals between inputs ✓
2. B common-mode signals applied equally to both inputs ✓
3. C signals on inverting input only without any gain ✓
4. D supply voltage variations as common-mode always without CMRR limit ✓