A feedback amplifier with closed-loop gain Acl = 10 has feedback fraction β = 0.1. What is the open-loop gain (A)?

The correct answer is B: 1000. From Acl = A/(1 + Aβ), we get 10 = A/(1 + A×0.1). Solving: 10(1 + 0.1A) = A → 10 = 0.9A → A ≈ 1000 (for high gain).

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

The correct answer is C: Dynamic current during charging/discharging of load capacitance. CMOS dynamic power = CV²f dominates; ideal CMOS has zero static power as pull-up and pull-down never conduct simultaneously.

A moving average filter y[n] = (x[n] + x[n-1])/2 has a zero at:

The correct answer is B: z = -1. H(z) = (1 + z^(-1))/2. Setting numerator to zero: 1 + z^(-1) = 0 gives z = -1.

In a cascaded 4-bit counter system where two 4-bit counters are connected, what maximum count value can be achieved?

The correct answer is B: 2⁸ - 1 = 255. Two cascaded 4-bit counters form an 8-bit counter system. Maximum count = 2⁸ - 1 = 255 (counts from 0 to 255, total 256 states)

A varactor diode is used in frequency modulation circuits because:

The correct answer is A: Its junction capacitance varies with reverse bias voltage. Varactor (variable capacitor) diodes have a depletion capacitance C_j = C_0/(1+|V_R|/V_bi)^n that varies with reverse bias. This voltage-dependent capacitance is used to modulate oscillator frequency.

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Electronics (ECE)
Digital Electronics

Analog/digital electronics, communication

11 Q 4 Topics Take Mock Test

Difficulty: All Easy Medium Hard 11–11 of 11

Topics in Electronics (ECE)

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

Q.11 Hard Digital Electronics

For a 3-bit Johnson counter, the maximum count is:

A 3

B 6

C 7

D 8

Correct Answer: B. 6

EXPLANATION

Johnson counter (twisted ring counter) has 2n states for n flip-flops. For 3-bit: 2×3 = 6 states. It's more efficient than ripple counter but less than binary counter.

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Electronics (ECE) Digital Electronics

Electronics (ECE)
Digital Electronics