How does an open collector output work?

How does an open collector output work?

An Open Collector output is an NPN transistor. An NPN transistor allows the sinking of current to common. It can be thought of as a switch that allows the circuit, after the load, to be connected to common. The voltage should be measured across the output load to determine if the open collector is working properly.

What is an open collector device?

An open collector output refers to an output that is connected to the collector of a transistor. Basically, just think of a transistor. A BJT transistor has a base, a collector, and an emitter. An open collector output is an output device that is attached to an open collector of a transistor.

What is an open collector buffer?

In an open collector buffer, you need a pull up resistor in order to give you a HIGH level output. With this pull up resistor, you’ve got two possible output levels: LOW (e.g. 0V) and HIGH (e.g. Vcc). If you don’t use any pull up resistor, you’ve got two possible output levels: LOW (e.g. 0V) and HIGH IMPEDANCE.

Is open collector sinking or sourcing?

While the NPN open collector transistor circuit produces a “current-sinking” output, that is the NPN transistors open collector terminal will sink the current to ground (0V), a PNP-type transistor can also be used in an open collector configuration to produce what is called a “current-sourcing” output.

Why is it called open collector?

One way to overcome this inversion of the transistors switching state is to remove the collector resistor, RC completely and have the transistors collector terminal available to be connected to some external load. This type of set-up produces what is commonly called an open collector output configuration.

What is open drain or open collector?

Open-Collector An “open collector” is functionally the same as an “open drain”. An “open collector” refers to a current sink on a BJT transistor output, while an “open drain” refers to a current sink on a FET output.