This circuit was obtained in a Popular Electronics of the 90s. The circuit uses integrated from the time, uncommon today. Note that the speaker has a higher impedance than ordinary speakers.
This circuit was found in the June 1991 issue of Radio Electronics magazine. The circuit uses two...
The MOSFETs are of the type of power and the resistors have their values between 1 k and 10 k for...
In the figure we have the way to use an LED to increase the voltage of a zener. The increase...