What is the fundamental relationship for an amplifier's voltage gain?

V_out = A_v × v_in, where A_v is the voltage gain

True or False: An ideal op-amp has infinite input impedance and zero output impedance.

True. Ideal op-amps have infinite input impedance and zero output impedance.

What are the two golden rules for ideal op-amps in negative feedback?
A) Infinite gain, zero offset
B) No input current, V+ = V-
C) High bandwidth, low noise
D) Unity gain, stable operation

B) No input current flows into terminals, and voltage difference between inputs is zero (V+ = V-)

The gain of an inverting amplifier configuration is _____.

A_v = -R_f/R_in

What happens to bandwidth when negative feedback is applied to an amplifier?

Bandwidth increases according to BW_f = BW(1 + Aβ)

Calculate the gain in dB for an amplifier with voltage gain of 100.

A_v(dB) = 20 log₁₀(100) = 40 dB

True or False: A common-emitter amplifier provides 180° phase shift between input and output.

True. Common-emitter configuration produces 180° phase shift between input and output signals.

Which amplifier class has maximum theoretical efficiency of 78.5%?
A) Class A
B) Class B
C) Class AB
D) Class C

B) Class B amplifiers have maximum theoretical efficiency of π/4 ≈ 78.5%

What is the transconductance formula for a MOSFET in saturation?

G_m = 2√(K_n × I_D) = 2I_D/(V_GS - V_TH)

The _____ frequency is where gain drops to 0.707 of midband value.

3-dB cutoff

What does CMRR measure in differential amplifiers?

Common-Mode Rejection Ratio measures ability to reject signals common to both inputs

True or False: Emitter followers have high input impedance and low output impedance.

True. Emitter followers (common-collector) have high input impedance and low output impedance.

For cascaded amplifiers, total gain equals
A) Sum of individual gains
B) Product of individual gains
C) Average of individual gains
D) Difference of individual gains

B) Product of individual gains: A_total = A₁ × A₂ × A₃ × ... × A_n

What is the Barkhausen criterion for oscillation in feedback amplifiers?

|Aβ| ≥ 1 and ∠(Aβ) = 360° (or 0°)

The maximum frequency for undistorted sinusoidal output is limited by _____.

Slew rate: f_max = SR/(2π × V_peak)

Calculate output of summing amplifier: R_f=20kΩ, R₁=10kΩ, V₁=0.5V, R₂=5kΩ, V₂=0.2V

V_out = -20k(0.5/10k + 0.2/5k) = -20k(0.05m + 0.04m) = -1.8V

True or False: Class A amplifiers have lower distortion but higher power dissipation than Class B.

True. Class A has low distortion but high power dissipation compared to Class B.

What happens to gain-bandwidth product when op-amp configuration changes?
A) Increases
B) Decreases
C) Remains constant
D) Becomes zero

C) Remains constant. GBW is an intrinsic op-amp characteristic that stays constant.

For voltage divider bias stability, R_TH should be _____ compared to βR_E.

R_TH ≤ 0.1βR_E for good bias stability

Why is negative feedback beneficial in amplifier design?

Stabilizes gain, increases bandwidth, reduces distortion, and controls input/output impedances

A differential amplifier with A_d=1000 and A_c=0.1 has CMRR of _____ dB.

CMRR = 20 log₁₀(1000/0.1) = 20 log₁₀(10,000) = 80 dB

True or False: Source followers in FET circuits are equivalent to emitter followers in BJT circuits.

True. Both provide unity gain, high input impedance, and low output impedance.

Which feedback topology increases both input and output impedances?
A) Voltage-series
B) Voltage-shunt
C) Current-series
D) Current-shunt

C) Current-series feedback increases both input and output impedances

What is the typical phase margin requirement for stable amplifier operation?

Phase margin > 45° typically ensures stable operation

An op-amp with GBW=2MHz configured for gain of 40 has bandwidth of _____.

BW = 2MHz/40 = 50 kHz

Calculate the closed-loop gain: A_OL=10,000, β=0.01

A_f = 10,000/(1 + 10,000×0.01) = 10,000/101 = 99.01

True or False: Common-base amplifiers provide current gain but no voltage gain.

False. Common-base provides voltage gain but no current gain (current gain ≈ 1).

What determines the lower cutoff frequency in amplifiers?
A) Transistor capacitances
B) Coupling capacitors
C) Load resistance
D) Supply voltage

B) Coupling and bypass capacitors determine the lower cutoff frequency f_L

For a BJT at room temperature, r_e approximately equals _____.

R_e ≈ 26mV/I_E where I_E is emitter current

An amplifier system needs gain of 1000. Design using two stages with equal gains.

Each stage needs gain = √1000 ≈ 31.6, since A_total = A₁ × A₂