CET Analog Electronics and Amplifiers Flashcards

What does the unity-gain bandwidth (GBW) of an op-amp represent?

Answer: The frequency at which the open-loop gain drops to 1 (0 dB)

Unity-gain bandwidth is the frequency where the op-amp's open-loop gain equals one, and it equals the gain-bandwidth product.

Which amplifier configuration is best suited for impedance matching between a high-impedance source and a low-impedance load without voltage gain?

Answer: Common-collector (emitter-follower)

The emitter-follower has near-unity voltage gain, very high input impedance, and low output impedance, making it ideal for impedance buffering.

What causes thermal runaway in a BJT power amplifier?

Answer: Increasing temperature raises collector current, which further raises temperature in a positive feedback loop

As junction temperature rises, ICEO increases, boosting IC, which generates more heat — a destructive positive feedback cycle called thermal runaway.

In a class AB push-pull amplifier, what is the main purpose of the bias diodes placed between the two transistor bases?

Answer: Provide a small forward bias to eliminate crossover distortion

Bias diodes hold each transistor slightly on so both transistors conduct near the zero-crossing, eliminating crossover distortion.

If an amplifier has a voltage gain of 50 and a bandwidth of 20 kHz, what is its gain-bandwidth product?

Answer: 1 MHz

GBW = gain × bandwidth = 50 × 20,000 Hz = 1,000,000 Hz = 1 MHz.

What type of distortion occurs when an amplifier output is driven beyond its linear region, flattening the peaks of the output waveform?

Answer: Clipping distortion

Clipping distortion occurs when the output voltage hits the supply rail limits, cutting off the peaks of the waveform.