This circuit was obtained from American documentation from the 1990s. The transformer can be a car ignition coil that works like an autotransformer. Q2 must be equipped with a heat sink.
We found this circuit in the Linear Applications Handbook published by National Semiconductor in...
In a September 1992 Radio Electronics article, we found this basic 555 circuit used to generate fixed...
In the figure we have a simple way to have a peak bargraph indicator. The amplifier is of the...