This step of two transistors has a high input impedance due to the use of FET. We can use BF245 for this function and the bipolar can be BC548. The circuit is from an 1975 American documentation.
Found in a 90s Electronic Design, this circuit provides a highly stable 60 Hz sine signal for...
This circuit is from an American publication of 1977. The tunnel diode admits equivalents and the...
This robot vision circuit was published in the December 1986 issue of Radio Electronics magazine. The...