A preset is a miniature potentiometer mounted directly on a printed circuit board. Unlike a standard volume knob meant for the end user, a preset is adjusted with a small screwdriver by a technician to calibrate a circuit, set a bias current, or tune a filter. Once set, it is usually left alone or sealed with a drop of glue.
Tweak the bias preset until you read exactly 50 milliamps across the emitter resistor.
Also heard as
- trimpot
- trimmer
Related terms
Potentiometer
A three-terminal variable resistor used to manually adjust voltage or resistance in a circuit.
Pot
A common shorthand for a potentiometer used to adjust resistance in a circuit.
Resistor
A passive two-terminal component used to limit current flow, divide voltages, or terminate transmission lines.
Bias
A steady DC voltage or current applied to an electronic component to establish its resting operating point.