Found in an American circuit manual from the 1970s, this circuit can use any general-purpose transistor. The operating frequency range is from 600 to 4000 Hz.
USB58xx and USB59xx Devices Integrate a 2:1 Multiplexer to Support Reversible Connection of USB...
This circuit, shown in the figure, consists of a variable gain amplifier with differential input...
This configuration can be applied to other transconductance operationals. The circuit has a gain...