Experiment 6 - The Alternative OR-Transistor Logic (RTL)

You can also represent the OR logic by negating the result of the NOR logic. In this case you have an alternative transistor circuit for the OR logic.

By using the NOR and NOT circuit, each of which consists of a single transistor, you can build this alternative OR-transistor circuit...

OR logic circuit consisting of NOR and NOT logic.

Alternative transistor circuit of an OR logic. (Enlarge)

Alternate circuit diagram of the OR logic with transistors.

In an OR-transistor circuit with two inputs, you have gained little using the alternative transistor circuit. Both circuits use two transistors.

On the other hand, you can build an OR-transistor circuit with multiple inputs and you still only need two transistors...

OR symbol with four input in circuit diagrams.

Circuit diagram of the OR logic with four inputs.

However, the resistor-transistor logic has some serious disadvantages...