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.
This ultrasonic insect repellent was found in American documentation from the 1980s. The...
This sophisticated circuit with a low, medium, and high treble filter is from 1990 documentation. The...
TTL square signals can be divided by 10 using this circuit. The maximum frequency depends on the...