A system with transfer function H(s) = (s+2)/(s²+3s+2) has poles at:

The correct answer is A: s = -1, -2. Denominator s²+3s+2 = (s+1)(s+2) = 0, giving poles at s = -1 and s = -2.

Which type of feedback configuration increases both input and output impedance?

The correct answer is D: Current-series feedback. Current-series (shunt-series) feedback increases both input impedance (series connection) and output impedance (current feedback). This is used in circuits requiring high impedances.

Which window function has the narrowest main lobe but highest side lobes?

The correct answer is A: Rectangular window. Rectangular window has the narrowest main lobe (~4π/N) but -13 dB side lobe level. Other windows trade main lobe width for lower side lobes.

The output of a system is y[n] = 0.5y[n-1] + x[n]. What is the transfer function H(z)?

The correct answer is A: 1/(1-0.5z⁻¹). From y[n] = 0.5y[n-1] + x[n], taking Z-transform: Y(z) = 0.5z⁻¹Y(z) + X(z). So H(z) = Y(z)/X(z) = 1/(1-0.5z⁻¹).

For maximum power transfer from a source to load through an amplifier, what should be the relationship between source and load impedance?

The correct answer is B: Zs = ZL* (complex conjugate match). Maximum power transfer theorem states that maximum power is delivered when load impedance equals complex conjugate of source impedance, especially in AC circuits.

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Electronics (ECE)

Analog/digital electronics, communication

187 Q 4 Topics Take Mock Test

Difficulty: All Easy Medium Hard 41–50 of 187

Topics in Electronics (ECE)

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

Q.41 Medium Signals & Systems

For a real signal x(t), its Fourier transform X(f) satisfies:

A X(-f) = X(f)

B X(-f) = X*(f)

C X(-f) = -X(f)

D X(f) = X(f)*

Correct Answer: B. X(-f) = X*(f)

EXPLANATION

For real signals, Fourier transform exhibits conjugate symmetry: X(-f) = X*(f)

Test

Q.42 Medium Signals & Systems

The inverse Fourier transform of δ(f-f₀) is:

A e^(j2πf₀t)

B cos(2πf₀t)

C sin(2πf₀t)

D e^(-j2πf₀t)

Correct Answer: A. e^(j2πf₀t)

EXPLANATION

IFT of δ(f-f₀) = e^(j2πf₀t) using sifting property of delta function

Test

Q.43 Medium Signals & Systems

A signal is called energy signal if:

A Its energy is infinite and power is zero

B Its energy is finite and power is zero

C Both energy and power are finite

D Its power is infinite

Correct Answer: B. Its energy is finite and power is zero

EXPLANATION

Energy signal has 0 < E < ∞ and P = 0. Power signal has P > 0 and E = ∞

Test

Q.44 Medium Signals & Systems

For a discrete-time LTI system with H(z) = 1/(1-0.5z⁻¹), the ROC should be:

A |z| < 0.5

B |z| > 0.5

C |z| = 0.5

D All z except z=0

Correct Answer: B. |z| > 0.5

EXPLANATION

For a causal system, ROC is outside the outermost pole. Pole at z=0.5, so |z| > 0.5

Test

Q.45 Medium Signals & Systems

A signal x[n] is time-reversed to get x[-n]. This operation is:

A Linear and time-invariant

B Nonlinear but time-invariant

C Linear but time-variant

D Neither linear nor time-invariant

Correct Answer: C. Linear but time-variant

EXPLANATION

Time reversal is linear (satisfies superposition) but time-variant (violates shift invariance)

Test

Q.46 Medium Signals & Systems

Which property does NOT apply to the Laplace transform?

A Linearity

B Time shifting

C Frequency shifting

D Periodicity preservation

Correct Answer: D. Periodicity preservation

EXPLANATION

The Laplace transform does not preserve periodicity of signals in the frequency domain

Test

Q.47 Medium Signals & Systems

The energy of signal x(t) = e^(-2t)u(t) is:

A 0.5 J

B 0.25 J

C 2 J

D 1 J

Correct Answer: B. 0.25 J

EXPLANATION

E = ∫₀^∞ e^(-4t)dt = [-e^(-4t)/4]₀^∞ = 1/4 = 0.25 J

Test

Q.48 Medium Signals & Systems

A system is BIBO stable if:

A ∑|h[n]| = ∞

B ∑|h[n]| < ∞

C All poles are in right half-plane

D Impulse response is periodic

Correct Answer: B. ∑|h[n]| < ∞

EXPLANATION

Bounded Input Bounded Output stability requires the impulse response to be absolutely summable: ∑|h[n]| < ∞

Test

Q.49 Medium Signals & Systems

The Fourier transform of a rectangular pulse rect(t/T) is:

A T·sinc(πfT)

B sinc(fT)

C T·sinc²(πfT)

D πT·sinc(fT)

Correct Answer: A. T·sinc(πfT)

EXPLANATION

The Fourier transform of rect(t/T) is T·sinc(πfT) where sinc(x) = sin(x)/x

Test

Q.50 Medium Analog Circuits

Which of the following statements about op-amp PSRR (Power Supply Rejection Ratio) is correct?

A PSRR is independent of frequency

B Higher PSRR indicates better rejection of power supply noise

C PSRR is measured in Ohms

D PSRR has no effect on output DC voltage

Correct Answer: B. Higher PSRR indicates better rejection of power supply noise

EXPLANATION

PSRR (in dB or V/V) measures how much power supply voltage variations appear at output. Higher PSRR (more negative in dB) = better rejection. PSRR varies with frequency and is crucial for low-noise applications.

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