Transistor XOR gate
An XOR Gate???
Don't be surprised if you don't know what that means... because we haven't mentioned XOR (exclusive OR) gates so far. But here's the project that lets us find out about this fascinating circuit....
An XOR gate is a logic circuit that produces an output 0 only when 1 and 0 signals are applied at the same time to two or more input terminals, and 1 when the input signals are same (both 1 or both 0).
We're going to make a transistor XOR gate and find out how it works. Note that the input signals are 1 when keys are pressed, and 0 when released. The output signal is 1 when the LED lights up, and 0 when the LED goes out.
Wire the project, turn power ON, and see what happens to the LED when you press and release S1 and S2. Figure 1 shows how this circuit works. Try following the current path on schematic.