Analog Electronics, Amplifiers and Operational Amplifiers — Practice

Question 1

State the ripple factor of half-wave and full-wave rectifiers.

Accepted Answer

1.21 for half-wave and 0.482 for full-wave.

Question 2

An inverting amplifier has Rf = 100 k and Rin = 10 k. Find the gain.

Accepted Answer

-10.

Question 3

A CE stage has IC = 1 mA and RC = 5 kilohm. Find gm and the voltage gain.

Accepted Answer

gm = 1 mA/26 mV = 38.5 mS. Av = -gm RC = -192.

Question 4

A non-inverting amplifier with Rf = 100 k and R1 = 10 k uses an op-amp with a 1 MHz gain-bandwidth product. Find the gain and bandwidth.

Accepted Answer

Gain 1 + 10 = 11. Bandwidth = 1 MHz/11 = about 91 kHz.

Question 5

A Wien bridge oscillator has R = 10 kilohm and C = 16 nF. Find its frequency.

Accepted Answer

f = 1/(2 pi x 1e4 x 16e-9) = 995 Hz.

Question 6

An op-amp has a slew rate of 1 V per microsecond. What is the largest 10 V peak sine frequency it can reproduce undistorted?

Accepted Answer

f = SR/(2 pi Vp) = 1e6/(2 pi x 10) = about 15.9 kHz.

Question 7

Which feedback topology raises input impedance and lowers output impedance, and what does it amplify?

Accepted Answer

Series-shunt (voltage series) feedback. It samples voltage and mixes in series, so it behaves as a voltage amplifier.

Question 8

What is the maximum efficiency of a class B push-pull amplifier?

Accepted Answer

78.5 percent.

Practice — Analog Electronics, Amplifiers and Operational Amplifiers