This circuit simulates the effect of an inductance. Equivalent operational amplifiers can be used, and the power supply must be symmetrical. The circuit is from a 90's Poptronics.
This circuit uses an old National Semiconductor operational amplifier, but it can be implemented with...
In this circuit the regulation is made from a circuit in the LED cathode. The configuration is...
For the component values used in thisf this circuit, the frequency can be adjusted between 740 Hz and...