The 2N3904’s PNP complementary type is 2N3906. 2N3904 transistor features Well suitable for tv and home appliance equipment Small load switch transistor with high gain and low saturation voltage Up to ...

You should choose transistors with low saturation voltages (such as 2N3904 for Q3 and MJE210 for Q1 and Q2). This minimum voltage will change with temperature, decreasing at higher but increasing at ...

The collector and the base of a 2N3904 transistor are connected together as shown in Fig. 2, and the bias current is set via the DC bias source at 1mA.