This high impedance amplifier is from 1985 documentation by General Electronic. The amplifier with FET at the entrance is from the period and the source is 9 V.
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...