What is the simplest way to make an AND gate using PNP transistors
A good way to build gates with limited numbers of transistors is to use RTL (resistor-transistor logic) techniques. For example, here is a NAND gate, which can be converted into an AND gate with an inverter:







simulate this circuit &ndash; Schematic created using CircuitLab

The fan-in and fan-out capabilities of this type of logic are not great, which is why it was abandoned once the development of ICs made the incremental cost of transistors essentially negligible. But it can be used to build moderately complex logic circuits if you don't care too much about the speed.