Open collector door (OC gate)

Open collector door

In Engineering PracticeThe function of parallel output of two doors to realize and logic is called line and.
Evaluate the knowledge. When the outputs of the two logical Gates shown in the figure are connected together, and the outputs of the first gate are high (T4 conduction of the first gate ), when the output of the second door is low (T3 conduction of the second door), a large current channel will appear in the middle red line, which may cause damage to the transistor.

In order to avoid high current in line and time, the open collector door (OC gate) can be used to solve the problem. Open collector is used to delete the voltage follower from the push-pull output level of the TTL and non-gate circuits, as shown in:

For an OC gate with two inputs, its symbols in the circuit can be expressed as follows:

To implement the Logic Functions of the line and line, you can add a public pull-up resistor RP between the power supply VCC and the power supply pole of the T3 output tube of multiple door circuits, as shown in. For the sake of conciseness, two oc-door parallel links are used as an example. The icon "" indicates the meaning of open collector.