This small amplifier with the fraction-watt LM4862 was found in the November 1999 issue of Electronics Now. The power supply is low voltage.
This circuit is from 1977 documentation, but can be assembled with BC548 for Q1, Q2 and Q4, BC558...
Found in American documentation from the 90s, this circuit uses components that are still common...
This high impedance input amplifier is suitable for the use with piezoelectric sources such as...