Article: Amplifiers Handle Small Signals.(auto-zero amplifier)

By Jon Titus, Contributing Editor

I encountered my first 'chopper' circuit in an old ignition spark coil. Basically, a buzzer chopped a dc current that passed through a coil. A separate step-up coil produced several thousand volts at low current. Good fun. Some old instrumentation systems chopped a low-amplitude dc signal to convert it to an ac signal. At the time, the dc characteristics of amplifiers weren't terribly good, so converting a signal to ac and running it through an amp made sense. A demodulator circuit at the amp's output produced an amplified dc signal.

The words 'chopper amplifier'no longer refer to a device that chops dc signals. ...