Open-Collector Output
In a component with an open-collector output,
the output of the integrated circuit is connected
with the base of an NPN transistor.
The emitter is connected to ground,
while the collector forms the new output of the circuit.
The operation is simple...
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The transistor is off in the LOW state.
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The transistor is on in the HIGH state
and the Open-Collector outout is
connected to ground.
The open collector output can be operated at a voltage
different from the supply voltage,
eg, when controlling relays.
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Illustration Open-Collector output.
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The open-collector output is also often used
where a large number of
logic outputs need to be connected.
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Timer 555
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Comparator LM311
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For C-MOS integrated circuits, the comparable output
is referred to as Open-Drain output.
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