Amplifiers
Circuits that increase the power of a signal, built from transistors in a handful of standard configurations.
An amplifier produces an output that is a larger copy of its input, using energy from the power supply. Important parameters: gain, bandwidth, input and output impedance, linearity/distortion, noise and efficiency.
Sub-topics (7)
Amplifier Gain and Decibels
Gain is the ratio of output to input; decibels express ratios on a logarithmic scale.
Common Emitter Amplifier
The classic BJT voltage amplifier — high gain with an inverted output.
Common Collector Amplifier
The emitter follower: voltage gain just under 1, high input impedance and low output impedance — a buffer.
Common Base Amplifier
Low input impedance, high voltage gain and excellent high-frequency performance.
Power Amplifier Classes
Class A, B, AB, C and D amplifiers trade linearity against efficiency.
Frequency Response and Bandwidth
How gain varies with frequency; bandwidth runs between the −3 dB points.
Feedback in Amplifiers
Feeding part of the output back to the input trades gain for stability, linearity and bandwidth.
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