Found in old American documentation, this circuit makes use of operational amplifiers from the 70s that are not common today.
This 65 MHz oscillator uses a special transistor from the time that admits an equivalent. The circuit is...
This circuit triggers producing a loud sound when a change in temperature is detected. The circuit...
This circuit is from a 1976 technical documentation. The FET can be MPF102 or BF245 and the coil...