This circuit was found on an 80's Ham Radio. The transistor admits equivalent. The circuit can generate 20 to 100 MHz signals operating at the fifth harmonic of the crystal.
This TTL decoder circuit for PC ports was found in a document from 1992. The power supply can be...
This circuit is from an old Popular Electronics, but it can be easily implemented nowadays, even...
The basis of this circuit is a CA3130 operational amplifier. The transistor can be BC548, and the...