Fundamentals of Electronics Flashcards

A capacitor is connected in series with a resistor to an AC source. As frequency increases, what happens to the capacitive reactance (Xc)?

Answer: Xc decreases

Capacitive reactance Xc = 1/(2πfC), so as frequency increases, Xc decreases.

In a biomedical device, a zener diode is used primarily to:

Answer: Regulate voltage

Zener diodes operate in reverse breakdown to maintain a stable reference voltage, making them ideal for voltage regulation.

What is the time constant (τ) of an RC circuit with R = 10 kΩ and C = 100 µF?

Answer: 1 second

τ = RC = 10,000 Ω × 0.0001 F = 1 second.

Which type of amplifier configuration provides both voltage gain and current gain but with a 180° phase shift?

Answer: Common emitter

The common emitter configuration inverts the output signal (180° phase shift) and provides both voltage and current gain.

In an ECG machine, the CMRR (Common Mode Rejection Ratio) specification is important because it:

Answer: Rejects 60 Hz power line interference

High CMRR allows the differential amplifier to reject common-mode noise such as 60 Hz interference from power lines while amplifying the ECG signal.

What is the function of a low-pass filter in biomedical signal processing?

Answer: Passes low frequencies and attenuates high frequencies

A low-pass filter allows signals below its cutoff frequency to pass while attenuating higher frequency components.

An op-amp in an inverting configuration has Rf = 100 kΩ and Rin = 10 kΩ. What is the voltage gain?

Answer: -10

Inverting amplifier gain = -Rf/Rin = -100kΩ/10kΩ = -10, where the negative sign indicates phase inversion.