HAM Radio Extra Class Test Practical Electronics Circuits Questions and Answers Flashcards

What is the primary purpose of a bleeder resistor in a power supply circuit?

Answer: To discharge filter capacitors when the supply is turned off

A bleeder resistor safely discharges stored energy in filter capacitors after the power supply is switched off, preventing electrical shock.

In a Class AB amplifier, what advantage does it offer over a Class B amplifier?

Answer: Reduced crossover distortion

Class AB biases both transistors slightly into conduction, eliminating the dead zone at the crossover point that causes distortion in Class B designs.

What is the function of a bypass capacitor placed across the emitter resistor in a common-emitter amplifier?

Answer: To increase AC voltage gain by shorting the emitter resistor at signal frequencies

The bypass capacitor provides a low-impedance path for AC signals around the emitter resistor, removing the negative feedback that reduces gain at signal frequencies.

Which component in a voltage regulator circuit provides the reference voltage for comparison?

Answer: A zener diode

A zener diode maintains a stable reference voltage across its terminals when reverse-biased, which the regulator compares against the output to maintain regulation.

What happens to the Q factor of a parallel resonant circuit if the resistance in the circuit increases?

Answer: The Q factor decreases

Q factor equals the ratio of reactive power to resistive power, so increasing resistance raises losses and reduces the circuit's Q factor.

What type of filter topology uses both series inductors and shunt capacitors to achieve a sharp cutoff response?

Answer: A pi-network low-pass filter

A pi-network filter uses a capacitor-inductor-capacitor arrangement that provides steeper rolloff than simple RC filters due to multiple reactive elements.