Audio Amplifiers With Two Transistor and Its Applications Jun 27, 2016Audio Amplifiers. The audio amplifiers are simple circuit diagrams used for the amplifying weak signals from the capacitive condenser microphone and this circuit is used for the sound sensing applications and also in automatic robotic sensors. In this audio amplifier we use two transistors which are BC547 and with some other components.Author: Tarun Agarwal Single Transistor Audio Amp - Hackster Apr 25, 2016Adding a simple single transistor audio amplifier will increase the volume and frequency response to the level we are accustom to. All of the circuits presented here will work with suitable performance with a Pinguino PIC chip. However, for optimum performance a circuit can be designed to maximize the PIC pin current capabilities.