The internal schematic diagram for a typical open-collector buffer is not much different from that of a simple inverter: only one more common-emitter transistor stage is added to re-invert the output signal. Its symbol is simply a triangle, with no inverting “bubble” on the output terminal: Buffer Gateįor this purpose, a special logic gate called a buffer is manufactured to perform the same function as two inverters. The logic level is unchanged, but the full current-sourcing or -sinking capabilities of the final inverter are available to drive a load resistance if needed.
Remember that gate circuits are signal amplifiers, regardless of what logic function they may perform.Ī weak signal source (one that is not capable of sourcing or sinking very much current to a load) may be boosted by means of two inverters like the pair shown in the previous illustration. While this may seem like a pointless thing to do, it does have practical application.
