Transistor Amplifier Saved

This amplifier circuit is comprised of two transistors, in a differential configuration. The output is at the collector terminals of the two transistors. A base terminal pull-up resistor supplies the zero frequency base current. The collector terminal bias voltage is set at half the supply voltage. It is 7.5 volts in this simulation. The circuit functions as a band pass filter. At each transistor, a high pass filter converts input voltage to a current. The current is amplified through the transistor. A low pass filter at the output of each transistor converts the current signal to a voltage signal. The pass-band gain is about equal to G=(B*R3)/R1, where B is the transistor current gain constant. In this circuit simulation, the pass band gain is set at 5 V/V. The combined differential gain is about 10 V/V. Although not necessary, a transformer is connected to the output for isolation and to re-reference the signal to ground.