This circuit was obtained from an American documentation from the 90's. The components can be changed, and a power step can be added for greater sound volume.
The figure shows how to use CMOS inverters as amplifiers. The circuit is from a Radio Electronics from...
This interesting circuit measures the distortion of the sinusoidal voltage of the power grid. We...
This circuit was found in an American publication from the 50's. The transistors are made of...