Found in American documentation, this circuit for modulated infrared signals can be tuned to a certain frequency. The photodiode can be of any type.
This circuit is from a documentation from the 70s. The transistors are types of germanium of the...
This circuit uses an operational amplifier that is still common today. The indication is made by...
We found this circuit in a 1986 documentation, however, by the components used it can still be...