The buffer amplifier is an important stage of any audio amplifier for proper matching between two stages as well as to match any high impedance transducers such as Electret Microphone, Carbon Microphone, Crystal Microphone, Crystal Pick-up Unit, Radio Tuner, Magnetic Pick-up, Digital signal Pick-up Unit etc.
The unique characteristics of the Buffer Amplifier is high input impedance and low output impedance and the gain is almost nil. We are describing the circuit of a two stage buffer amplifier in the attached LINK.
DESCRIPTION: The first stage of the buffer amplifier works as a common emitter configuration with a large amount of feedback and the second stage is an emitter follower. This ensures a high input impedance of about 3.5 Meg Ohms to 3.7 Meg Ohms and the output impedance shall be as low as 250 Ohms. The voltage gain is unity and the frequency response at -3dB point shall be from 20 Hz to more than 20 KHz. The distortion shall be below 0.5% with output voltage up to 2.5V. The curve mentioned below shows the distortion level corresponding to output voltage.