This circuit was found in a documentation of the 80s, having didactic purpose. For R1 values between 10k to 1M can be used. Transistors are general purpose types.
This circuit has a traditional configuration often found on this site. The transistor must be...
This is a typical common emitter amplifier stage configuration. The transistor can be used...
We found this circuit in a 1983 English magazine, but it can be easily assembled with the BC548 or...