Amplifier with variable gain outside dead zone - has positive feedback and loop containing two antiseries Zener diodes

摘要

The amplifier consists of an operational amplifier IC with its inverting input coupled via a feedback resistor to its output. The output is connected over two anti-series zener diodes (12, 14) in the positive feedback path to a second resistor coupled to the amplifier's non-inverting input. The output signal is taken from the zener diode/second resistor junction. The advantage lies in the simplicity of the circuit. The amplifier has a dead zone for both polarities, and can be used as a comparator or Schmitt trigger with adjustable hysteresis. Four resistors are provided: a feed (4), a feed back (6), a linking (8), and a voltage divider (10).