C-MOS XOR gate


Back in project Transistor XOR gate you saw how an XOR gate works.

Since we've made up other digital circuits by combining NAND gates, you might suspect we could make XOR gates as well. We can, as this project shows.

After you finish the wiring connections, turn power ON and press S1 - does anything happen to LED 1 ?

Now release S1 and press S2. What does LED 1 do now?

While keep pressing S2 press S1. What happens to LED1?

You can see this circuit behaves like the XOR gate you built back in project Transistor XOR gate.

The output is 1 as long as the inputs are different. But if both inputs are the same -either 0 or 1 - the output of the gate is 0. Put on your thinking cap and try to follow each 0 or 1 input through the circuit until you reach the output. It will help if you mark "0" or "1" on the schematic at the input and output of each NAND gate.








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