This is a transistor amplifier circuit diagram. here in this diagram used 2 transistors, 2sc5200 and 2sa1943. this is a PNP and NPN transistor amplifier circuit diagram. in this circuit, we also can use another PNP and NPN transistor. NPN is a positive transistor and NPN is a negative transistor. Here we used 2sc5200 and 2sa1943 transistors. this is very common transistor in the Audio world. we used so much this transistor.