This circuit has a type of bias called "virtual earth" providing good gain, given by R2. The circuit is from a 1985 publication may be used with commonly used transistors such as BC548. The circuit is for low intensity signals. Power must be made with a source of excellent filtration. One application of this circuit is as audio amplifier or signal up to a few hundred kilohertz. Low noise transistors like the BC549 are suitable for sensitive audio applications.
