CET Staging & Prognostic Factors 3

Question 1

Which factor most significantly determines the input impedance of a common-emitter transistor amplifier stage?

Accepted Answer

Base bias resistors and transistor beta

Answer

The input impedance of a CE stage is primarily set by the parallel combination of bias resistors and the transistor's beta times the emitter resistance.

Question 2

An amplifier stage has an output impedance of 10 kΩ driving a load of 1 kΩ. What happens to the voltage across the load relative to the open-circuit output voltage?

Accepted Answer

It drops significantly due to loading

Answer

The load forms a voltage divider with the output impedance; with a 10:1 ratio, most voltage drops across the internal impedance.

Question 3

What is the function of a buffer stage inserted between two amplifier stages?

Accepted Answer

Provide high input impedance and low output impedance to prevent loading

Answer

A buffer stage (often an emitter or source follower) presents high input impedance and low output impedance to isolate stages and prevent loading effects.

Question 4

In a cascaded amplifier system, thermal noise contributed by each stage:

Accepted Answer

Accumulates and is amplified by subsequent stages

Answer

Noise introduced in early stages is amplified along with the signal by all subsequent stages, making the first stage's noise contribution most critical.

Question 5

What is the significance of the 'noise figure' (NF) in a multistage receiver front-end?

Accepted Answer

It measures how much the stage degrades signal-to-noise ratio

Answer

Noise figure quantifies the degradation of SNR as a signal passes through the amplifier stage; lower NF means less added noise.

(CET) Certified Electronics Technician Practice Test

(CET) Certified Electronics Technician Practice Test

CET Staging & Prognostic Factors 3