This circuit was found in a 1967 Electronics World. We can design it with a BF245 for the FET and a BC558 for the bipolar transistor. The circuit has 3 scales and a 10 M ohm input resistance.
The transistors for this circuit from an 80's documentation can be the BC548 or 2B222 and the...
In the figure we show a timer, which is simpler because it uses only one of the four gates of the...
This circuit checks the infrared emission of a common remote control. We found it in the March 1993...