HAM Practical Circuits and Components 4

Question 1

What is the purpose of neutralization in an RF amplifier?

Accepted Answer

To cancel the feedback through the transistor's internal capacitance that can cause oscillation

Answer

Neutralization feeds a portion of the output signal back in opposite phase to cancel the feedback through Cgd or Cbc, preventing self-oscillation.

Question 2

Which type of amplifier configuration is commonly used in the front end of a receiver to provide gain with minimum added noise?

Accepted Answer

Low-noise amplifier (LNA) using a GaAs FET or similar low-noise device

Answer

LNAs using GaAs FETs or modern low-noise transistors are designed to add minimal thermal noise while providing useful gain at RF frequencies.

Question 3

What is the advantage of a differential amplifier input stage in an operational amplifier?

Accepted Answer

It rejects common-mode signals (noise present on both inputs equally) while amplifying the differential signal

Answer

The differential pair rejects common-mode interference (like power supply noise or EMI) that appears equally on both inputs, amplifying only the difference between them.

Question 4

A voltage doubler rectifier circuit produces approximately what output DC voltage compared to the AC input RMS voltage?

Accepted Answer

Approximately twice the peak voltage (2.828 × RMS)

Answer

A voltage doubler charges two capacitors in series, each to the peak voltage, yielding approximately twice the peak (or about 2.83× RMS) at no load.

Question 5

What is the principal cause of intermodulation distortion (IMD) in an RF amplifier?

Accepted Answer

Non-linearity in the amplifying device creating sum and difference products of input signals

Answer

Non-linear transfer characteristics cause two or more input signals to mix, creating unwanted intermodulation products at frequencies like 2f1-f2 that fall within the passband.

HAM - Radio Extra Class Test Practice Test

HAM - Radio Extra Class Test Practice Test

HAM Practical Circuits and Components 4