FAQ
TL;DR: Typical DAC modules span 6–24 bits, and as one user noted, “ideal voltage source he hy.” This FAQ compiles thread‑proven answers on Fourier, ROC, modulation, LTI, damping, and RLC to speed up test prep. [Elektroda, iqbal sayed, post #21674351]
Why it matters: If you’re cramming for signal/control/DSP MCQs, these concise, sourced checkpoints cut confusion fast and reduce last‑minute errors.
- Period of an “infinite” continuous Fourier series is infinite; don’t overthink the symbol choices. [Elektroda, EMMR EMMR, post #21674295]
- At RLC resonance, net reactance is zero; the impedance equals R for maximum real power transfer. [Elektroda, iqbal sayed, post #21674329]
- Fastest response without overshoot is critically damped; underdamped always overshoots. [Elektroda, John Carter, post #21674297]
- For higher raw data rates among listed schemes, pick QAM over AM/FM/QPSK. [Elektroda, Ali Waqas, post #21674307]
- Ideal voltage source = constant voltage regardless of load current; great theory, not real hardware. [Elektroda, iqbal sayed, post #21674351]
Quick Facts
- Fourier “infinite series” period: infinite (matches MCQ key 1=c). [Elektroda, EMMR EMMR, post #21674295]
- RLC at resonance: X_L = X_C, so Z = R and net reactance = 0. [Elektroda, iqbal sayed, post #21674329]
- No‑overshoot fastest step response: critically damped (pick c when offered). [Elektroda, John Carter, post #21674297]
- Among AM/FM/QPSK/QAM, QAM carries the highest bits/s per Hz in the list. [Elektroda, Ali Waqas, post #21674307]
- “Ideal voltage source” provides fixed V independent of I; real sources approximate it. [Elektroda, iqbal sayed, post #21674351]
What’s the period of an infinite continuous Fourier series?
Infinite. For MCQs, when options include N, N+M, infinity, or 2π/n, choose “infinite” for an infinite continuous Fourier series. [Elektroda, EMMR EMMR, post #21674295]
Which modulation in the list has higher data rates: AM, FM, QPSK, or QAM?
QAM. It maps multiple bits per symbol and, within the given options, supports the highest raw data throughput for a fixed symbol rate. [Elektroda, Ali Waqas, post #21674307]
How is an LTI system uniquely characterized for analysis?
By its impulse response. Measure or model h(t) or h[n], and use convolution with the input to predict the output. [Elektroda, EMMR EMMR, post #21674295]
What exactly is a transfer function in control/signal problems?
A mathematical model that relates input to output in the transform domain (Laplace or z). It abstracts physical details into poles and zeros. [Elektroda, EMMR EMMR, post #21674296]
What’s the fastest achievable step response without overshoot?
Critically damped. It reaches the target quickly with zero overshoot; underdamped is faster initially but overshoots. “Pick critically damped when ‘no overshoot’ is stated.” [Elektroda, John Carter, post #21674297]
Does stability hold if the system’s z-transform is within the ROC?
Yes. If the system’s response lies in the ROC, the MCQ key flags it as stable; choose “system is stable.” [Elektroda, EMMR EMMR, post #21674295]
At resonance, what happens to net reactance in an RLC circuit?
Net reactance becomes zero; impedance equals R. Current peaks for a given applied voltage, enabling maximum real power in the resistor. [Elektroda, iqbal sayed, post #21674329]
Which theorem is often used for quick fault or network analysis in MCQs?
Superposition theorem. It simplifies multi-source circuits by summing individual source effects with others turned off appropriately. [Elektroda, iqbal sayed, post #21674336]
What sampling period avoids distortion per Nyquist criteria in the given MCQ?
Half the maximum signal period (i.e., sample at least twice the highest frequency). Select “half the max period.” [Elektroda, iqbal sayed, post #21674349]
Which amplifier class do preamps use for high linearity?
Class A. “Class A is highly linear” for small-signal stages, trading efficiency for distortion performance. [Elektroda, iqbal sayed, post #21674351]
Which system demands more stability margin among typical options?
A motor with position control. Precision positioning is sensitive to instability, so it needs higher stability margins. [Elektroda, iqbal sayed, post #21674349]
What is an ideal voltage source in one line?
A source that maintains constant voltage regardless of the current drawn; it’s a theoretical construct. [Elektroda, iqbal sayed, post #21674351]
When is power consumption maximum in an RLC circuit?
At resonance. With reactive parts canceling, power delivered to the resistor peaks for a given voltage. [Elektroda, iqbal sayed, post #21674336]
How many bits do common DAC modules offer in practice?
Typical modules range from 6 to 24 bits; exam keys often expect a value in that span. [Elektroda, iqbal sayed, post #21674349]
Quick how-to: check an MCQ on LTI stability using ROC/unit circle
- Read if the ROC includes the unit circle (discrete-time).
- If the stated response lies inside the ROC, select “stable.”
- If “no unit circle in ROC” appears, beware: it flags instability in many keys. [Elektroda, EMMR EMMR, post #21674295]
