Prof. Dr. Thorsten Jungmann (last updated 2026-10-03)
Otto Herbert Schmitt (1913–1998) was an American inventor, engineer and biophysicist. He is known for his scientific contributions to biophysics and for establishing the field of biomedical engineering. Schmitt coined the term ‘biomimetics’ and invented or co-invented the Schmitt trigger, the differential amplifier and the chopper-stabilized amplifier. In 1953 he was elected a Fellow of the American Physical Society, and in 1972 he was awarded the John Price Wetherill Medal.
Schmitt invented the Schmitt trigger (German: Schmitt-Trigger) in 1934 while he was a graduate student and published it in 1938 as ‘A thermionic trigger’. It was a direct result of his study of neural impulse propagation in squid nerves. Today a Schmitt trigger is a comparator circuit with hysteresis (German: Schalthysterese), implemented by applying positive feedback to the non-inverting input of a comparator or differential amplifier. It is an active circuit that converts an analogue input signal into a digital output signal. In the non-inverting configuration, the output is high when the input is higher than a chosen threshold and low when the input is below a different, lower threshold; between the two thresholds the output retains its value. This dual threshold action is called hysteresis: between the two thresholds the output keeps its previous value, so the circuit has memory.
Schmitt triggers are typically used in signal conditioning to remove noise from signals in digital circuits, particularly mechanical contact bounce in switches. The circuit is named a trigger because the output retains its value until the input changes sufficiently to cause a change.
Reference and further reading:
https://en.wikipedia.org/wiki/Otto_Schmitt
https://en.wikipedia.org/wiki/Schmitt_trigger