# ANSI open-collector inverter

Canonical URL: https://eloragrid.ai/symbols/ansi-open-collector-inverter
Publisher: Elora Grid
Updated: 2026-10-28
Lookup label: OC-NOT
Drawing use: Schematic
Reference families: IEEE / ANSI, Manufacturer

## Symbol convention

Convention: IEEE / ANSI
Form: Inverter triangle with bubble and open-circuit output marking
Distinctive-shape form as used in IEEE/ANSI-style schematics and manufacturer data books. Independent educational drawing; exact standard geometry and compliance are not asserted.

Inverter triangle with output bubble and an open-circuit mark, needing an external pull-up to produce a high level.

## In plain English

### What does ANSI open-collector inverter mean?

This is an inverter whose output transistor can only pull low. On distinctive-shape schematics the triangle and bubble are retained and an open-collector or open-drain mark, often the underlined diamond, is placed inside or beside the outline. A pull-up resistor or load to a supply completes the circuit.

### A simple example

Open-drain inverters are used to drive indicator LEDs, relay inputs and shared interrupt or alarm lines, and to translate to a higher pull-up voltage within the device rating. The schematic should show the pull-up value and its supply rail next to the gate.

### What the drawings help you do

The output state with no pull-up is undefined when the transistor is off. A drawing that omits the pull-up is incomplete even though the gate symbol is correct.

### This particular reference

Inverter triangle with output bubble and an open-circuit mark, needing an external pull-up to produce a high level. The non-inverting open-collector buffer has no output bubble.

### Terms

- Normally open / normally closed: The contact state in the normal condition defined for the drawing.
- Coil: A wound conductor that can produce a magnetic field when energised.
- Signal: Electrical information passed between devices, rather than necessarily the main power supply.

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.

- [SNx4HC05 hex inverters with open-drain outputs](https://www.ti.com/lit/ds/symlink/sn74hc05.pdf)
- [Overview of IEEE Standard 91-1984: explanation of logic symbols (SDYZ001A)](https://www.ti.com/lit/ml/sdyz001a/sdyz001a.pdf)


## What it represents

This is an inverter whose output transistor can only pull low. On distinctive-shape schematics the triangle and bubble are retained and an open-collector or open-drain mark, often the underlined diamond, is placed inside or beside the outline. A pull-up resistor or load to a supply completes the circuit.
Open-drain inverters are used to drive indicator LEDs, relay inputs and shared interrupt or alarm lines, and to translate to a higher pull-up voltage within the device rating. The schematic should show the pull-up value and its supply rail next to the gate.
The output state with no pull-up is undefined when the transistor is off. A drawing that omits the pull-up is incomplete even though the gate symbol is correct.

## How to read it

- Find the pull-up or load; without it the high level is undefined.
- Check whether the output is shared with other open-collector outputs.

## Information to show or reference

- Mark the open-collector or open-drain output.
- Show the pull-up and its supply.
- Record the maximum output voltage and sink current from the datasheet.

## Important distinction

The non-inverting open-collector buffer has no output bubble.

## Facts

- Output stage: Open collector or open drain
- External part: Pull-up resistor or load
- Artwork scope: Original educational illustration; consult the applicable standard and the selected device documentation for the exact graphic

## Public references

- [SNx4HC05 hex inverters with open-drain outputs](https://www.ti.com/lit/ds/symlink/sn74hc05.pdf) — Texas Instruments. Manufacturer documentation for inverters with open-drain outputs.
- [Overview of IEEE Standard 91-1984: explanation of logic symbols (SDYZ001A)](https://www.ti.com/lit/ml/sdyz001a/sdyz001a.pdf) — Texas Instruments. Open-collector output qualifier.

## 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.