Push-Pull Amplifiers

1.Transistors: Three similar npn BJTs, for example, 2N2925, 2N2924, or 2N2712.2.Resistors: One 680 kΩ, two 3.3 kΩ, two 1 kΩ, two 680 Ω, and one to be determined experimentally.3.Capacitors: Three 0.1 µ F (not electrolytic).4.Potentiometers: Two 100 kΩ.5.Output transformer: Transistor push-pull type. Two identical ordinary output transformers, without center-tapped primaries, could be used if connected in series. In that case the junction between the two primaries of the transformers would serve as the center tap. The secondaries of the two transformers would be connected in series and serve as one secondary. These secondaries would have to be connected in series in such a way that the output voltages would be in series.6.Power supply: One that puts out both polarities of dc voltage of equal magnitudes of about +15 and -15 V. Four 9-V transistor batteries, connected in series with the middle junction grounded, could be used. All dc voltages, including the base voltages for Q2 and Q3, can be taken from one power supply.7.Resistor substitution box.8.Function generator: Or other sine wave generator.