DTL Exclusive OR gate

An exclusive OR gate???

Don't be surprised if you don't know what that means because we haven't mentioned exclusive OR (abbreviated XOR) gates so far.

But heie's a Project that will let us find out about this fascinating circuit As you build this circuit, he sure the Select Switch is set to B.

When you finish the wiring connections, turn power ON. See what happens to LED 1.

Now press the Key, Any change in LED 1?

Release the Key and set the Select Switch to A. What does LED 1 do now?

Leave the Select Switch at A and press the Key. Notice anything different now?

Surprised at anything? Sure you were you didn't expect LED 1 to go out (or go to 0) when both, inputs were 1, did you? (Unless, of course you looked at the schematic for this Project very carefully before building it!)

So you can see that an XOR gate has an output of 0 if both inputs are the same. If the inputs air different (0 and 1 or 1 and 0), then the output is 1.

You can see that this is a handy circuit to let us know if we have two inputs that are the same. (Or to let us know if we have two different inputs).

There's also an XNOR gate (exclusive NOR). We won't build one here, but maybe you can figure out how, since it's the same thing as a NOR gate followed by an inverter! (Thai ought to tell you kovs an XNOR gate should work.)

Be sure to keep track of what you do in your notebook if you decide to design an XNOR gate.