This circuit has a frequency range of 30 Hz to 100 kHz with an output signal of 1 Vrms. We found it in 70s American documentation. The integrated circuits are CA3140.
We found this configuration in the Linear Applications Handbook of the National Semiconductor of...
This circuit is an application for an operational amplifier with field effect transistors from...
This circuit was found in an old Radio Electronics, but can still be assembled as the components are...