This amplifier with gain control was obtained in a documentation from Signetics of the 80's. Transistors are of power and operational amplifiers are not common nowadays.
This simple metal finder uses a 100 uA indicator. The exploration coil must be constructed in a...
This resistance meter has a linear scale, converting resistances to voltage. The operational...
This circuit was found in a 1995 documentation. Its purpose is to indicate voltage levels that are...