Walkthrough for fabricating a 2 input NAND gate using two BC547 NPN transistors.
1 470 Ohm resistor.
2 1k resistors. (Alternatively 3 1k resistors).
2 BC547 transistors.
Simple schematic wired up in Eagle CAD.
Here Pins 1 and 2 of the I/O header pins are Inputs and Pin 3 is the Output. I have used the Sparkfun Eagle libraries for my various components. Pin 4 is GND and 5 is Vcc.