This high impedance step suggested by an English publication can operate up to 1 MHz with 1 V rms output. Input impedance is 1 M ohm.
This touch switch is from a 1978 publication. The circuit should not be powered by a...
The circuit shown uses the 741 operational amplifier, but lower noise and higher gain equivalents...
We found this zener regulator in a 1978 radio amateur documentation. The operational can be...