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ANALOG BASICS

Transistor Signal Amplification

by James Antonakos

Start ý In The Beginning There Was Biasing ý Getting Signals In And Out ý The Big Capacitor ý A Close Look Inside • Loading the Amplifier • Is This the Right Frequency? • Yes, But Op-Amps are Easier • Sources and PDF

YES, BUT OP-AMPS ARE EASIER

Sure they are. I love them. To make an inverting amplifier you need only two resistors and an op-amp, plus either a split power supply or two more resistors for bias. Unlike the common emitter amplifier, you will know the exact gain because itýs based on using massive amounts of negative feedback that negates the effects of the raw device gain. Even better, the op-amp can be designed to work all the way down to DC and not have a lower cutoff frequency. The tradeoff is a much lower upper-frequency limit, but this is not usually a problem for audio designs.

The true benefits of the op-amp are clear only after exposure to the common emitter amplifier. Even so, if you look inside the op-amp, what do you see? Transistors.

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