This circuit was obtained from the March 1994 Electronics Now magazine. The circuit uses a common transistor which can be a low noise type such as the BC549.
This circuit is from an English magazine of 1977. The circuit is still current, just using BC547...
This circuit was obtained in an old Elektor. It is a reference, since the integrated products of the...
This circuit was found in a European technical documentation from 1991. It is a circuit that must...