# Op-amp comparator with hysteresis

Canonical URL: https://eloragrid.ai/symbols/op-amp-hysteresis-comparator
Publisher: Elora Grid
Updated: 2026-10-28
Lookup label: COMP-H
Drawing use: Schematic
Reference families: Manufacturer

Comparator or op-amp with positive feedback to the plus input, creating two switching thresholds.

## In plain English

### What does Op-amp comparator with hysteresis mean?

Adding a resistor from the output to the non-inverting input of a comparator gives positive feedback, so the switching threshold depends on the current output state. The result is hysteresis: the circuit switches at one level on a rising input and a lower level on a falling input, rejecting noise near the threshold.

### A simple example

This circuit is used for level detection from slow analogue signals such as temperature, battery voltage or tank level. The drawing should state both thresholds, or the resistor values and reference from which they are derived.

### What the drawings help you do

The circuit symbol does not show the thresholds directly and they depend on output swing, so a part with rail-to-rail or open-collector output changes the calculation.

### This particular reference

Comparator or op-amp with positive feedback to the plus input, creating two switching thresholds. An op-amp amplifier uses negative feedback to the minus input; this circuit uses positive feedback.

### Terms

- Signal: Electrical information passed between devices, rather than necessarily the main power supply.
- Rating: A value stating the conditions for which equipment is specified.
- Schematic: A drawing showing function and connections rather than physical appearance.

Concept diagram: Identify the device and form → Read the connections and state → Check the equipment reference
A guide to reading this reference. The original symbol illustration and its drawing notes appear below; these boxes are not a wiring diagram.

- [TLV3201 — voltage comparison](https://www.ti.com/product/TLV3201)
- [University tutorials: amplifier configurations and signal processing](https://wiki.analog.com/university/courses/tutorials/index)


## What it represents

Adding a resistor from the output to the non-inverting input of a comparator gives positive feedback, so the switching threshold depends on the current output state. The result is hysteresis: the circuit switches at one level on a rising input and a lower level on a falling input, rejecting noise near the threshold.
This circuit is used for level detection from slow analogue signals such as temperature, battery voltage or tank level. The drawing should state both thresholds, or the resistor values and reference from which they are derived.
The circuit symbol does not show the thresholds directly and they depend on output swing, so a part with rail-to-rail or open-collector output changes the calculation.

## How to read it

- Feedback to the plus input indicates hysteresis, not gain.
- Thresholds depend on output swing.

## Information to show or reference

- Show the positive feedback resistor and reference.
- State both switching thresholds.
- Show the output pull-up if the comparator is open collector.

## Important distinction

An op-amp amplifier uses negative feedback to the minus input; this circuit uses positive feedback.

## Facts

- Feedback: Positive, to the non-inverting input
- Result: Two switching thresholds
- Artwork scope: Original educational illustration; consult the applicable standard and the selected device documentation for the exact graphic

## Public references

- [TLV3201 — voltage comparison](https://www.ti.com/product/TLV3201) — Texas Instruments. Manufacturer comparator documentation.
- [University tutorials: amplifier configurations and signal processing](https://wiki.analog.com/university/courses/tutorials/index) — Analog Devices. Public tutorial material on comparator and feedback configurations.

## Graphic scope

Independent original educational concept illustration by Elora Grid. Not a certified standards graphic or manufacturer footprint. Unitless; not to scale. Original artwork licence: https://creativecommons.org/licenses/by/4.0/. Publisher material is linked only.