Found on an 80's Radio Electronics, this circuit is designed to pass the 300 to 34,000 Hz voice range using standard operational amplifiers.
In fact, the maximum output current of this source depends on the transformer which can be 6, 7.5, 9...
The figure shows a way to apply gain control to the LM3600 OTA. The circuit is from a Radio...
This application consists of a circuit that trips when the sensor resistance drops below a few...