OC-BUF
Open-collector buffer
Provides a logic output through a transistor pull-down stage requiring the documented external load or pull-up.
Schematic
IEEE / ANSI · WIRED-AND
ANSI wired-AND connection
Several open-collector outputs joined on one pulled-up line, so any output pulling low makes the line low.
In plain English
What does ANSI wired-AND connection mean?
A wired-AND connection is formed by joining open-collector or open-drain outputs to a single line with one pull-up. The line is high only when every output is off, so in positive logic the result is the AND of the individual output states. Some schematics draw a small AND outline around the junction to make the implied function visible.
A simple example
Shared interrupt lines, ready signals and I2C-style buses rely on this arrangement. A drawing should show every output on the net, the single pull-up, and the supply, because adding or removing a driver changes the logic and the pull-up current.
What the drawings help you do
The connection only works with open-circuit outputs. Joining push-pull outputs in the same way causes contention and possible damage, so the output type of each gate must be checked.
This particular reference
Several open-collector outputs joined on one pulled-up line, so any output pulling low makes the line low. A wired-OR uses open-emitter outputs with a pull-down; wired-AND uses open-collector outputs with a pull-up.
- Terminal
- An identified point where a conductor connects.
- Signal
- Electrical information passed between devices, rather than necessarily the main power supply.
- Rating
- A value stating the conditions for which equipment is specified.
Read the source: Overview of IEEE Standard 91-1984: explanation of logic symbols (SDYZ001A) · SNx4HC05 hex inverters with open-drain outputs
IEEE / ANSI · Open-collector outputs joined to a common pulled-up line
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.
Shown as an independently authored educational illustration. Use the cited publication and drawing legend to verify the required drafting form.
Schematic · WIRED-AND
What it represents
A wired-AND connection is formed by joining open-collector or open-drain outputs to a single line with one pull-up. The line is high only when every output is off, so in positive logic the result is the AND of the individual output states. Some schematics draw a small AND outline around the junction to make the implied function visible.
Shared interrupt lines, ready signals and I2C-style buses rely on this arrangement. A drawing should show every output on the net, the single pull-up, and the supply, because adding or removing a driver changes the logic and the pull-up current.
The connection only works with open-circuit outputs. Joining push-pull outputs in the same way causes contention and possible damage, so the output type of each gate must be checked.
How to read it
- Check that every joined output is open collector or open drain.
- There should be one pull-up for the whole net.
Information to show or reference
- Show all contributing outputs on the shared net.
- Draw a single pull-up with its value and supply.
- Mark the open-circuit output type on each driver.
A distinction that matters
A wired-OR uses open-emitter outputs with a pull-down; wired-AND uses open-collector outputs with a pull-up.
Sources you can follow
These public references support the explanation and provide further detail. Their graphics and downloadable files remain with their publishers.
Overview of IEEE Standard 91-1984: explanation of logic symbols (SDYZ001A)
States that open-collector outputs are capable of positive-logic wired-AND connection.
SNx4HC05 hex inverters with open-drain outputs
Manufacturer open-drain output documentation.
About this graphic
This illustration was authored independently by Elora Grid to explain the concept. It is not reproduced from a customer drawing, an official standard graphic or a manufacturer CAD file. Its correspondence to an exact IEC or IEEE symbol identifier has not been certified.
SVG and DXF downloads contain this original artwork. DXF uses unscaled drawing units; a GA envelope supplies no product dimensions, clearances or fabrication information. Original artwork is available under CC BY 4.0. Third-party references retain their own terms.
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IEC open-circuit output, L-type (open collector)
Underlined diamond inside an outline: an open-circuit output that can only drive a low level.
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