Open Drain or Open Collector Configuration

[AbhinavRajan]

I am finding very difficult and confusing to understand the concept of The Open Dain or Open collector configuration.
Can someone explain in clear and simple English with an example.

 

[KlausST]

Hi,

A open collector (or open drain) circuit needs a resitor as pullup.
The bjt switches to GND, when activated.
The resistor limits the current to a safe value and pulls the voltage to VCC when the bjt is not activated.

The benefit is, that there will never be a short circuit condition (with high current) when multiple open collector outputs are connected, independent of the states.

The current is limited by the resistor, independent how much outputs are active or not.

***
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Klaus