This amplified speaker is from a Radio Electronics from September 1988. The power integrated circuit is from that time and the other components are still common today.
This circuit was obtained in a 1989 English magazine. Despite using a fixed 5 V regulator, it can...
With the feedback of the output circuit, the monostable acts as a frequency divider, that is, it...
In this circuit of an old American documentation, the input impedance is the same as the output...