Operational Amplifier Fundamentals Unit 8 – Voltage Comparators
UNIT 8 – VOLTAGE COMPARATORS
UNIT OBJECTIVE
At the completion of this unit, you will be able to describe the operation of an operational
amplifier comparator circuit.
UNIT FUNDAMENTALS
A voltage comparator circuit compares an input voltage to a reference voltage and indicates
whether the input is greater than, equal to, or less than the reference voltage.
Voltage comparators are typically used as level detectors or squaring circuits.
Level detectors indicate when a voltage crosses a specific set point. Squaring circuits convert
slow rise or fall time wave-forms into high slewing waveforms.
On this open-loop comparator, VI is compared to the reference voltage (VREF). VREF is
connected to the non- inverting terminal of U1. Therefore, U1 is not zero based, but has a trigger
point equal to VREF.
In this circuit, U1 tends to saturate due to the very high open-loop gain. VD is not 0V if U1 is
saturated.
When VI is more positive than VREF, VD is greater than 0V, and VO switches to -VSAT.
When VI is more negative than VREF, VD is greater than 0V, and VO switches to +VSAT.