The circuit shown is from Texas Instruments optoelectronics documentation. The input signal is audio and equivalent LEDs can be used. Other operational amplifiers can also be used.
Found in an old English publication this circuit uses a dual gate MOSFET. Coils not specified....
An oscillator that can be frequency controlled by a resistive sensor is shown in the figure. The...
Using a 741 op amp with symmetrical source, this circuit was found in a 1982 documentation. The...