infrared transmitter

7-02 elektor july/august 1980 This is a very simple circuit and is really intended for hobbyists who like experimenting with infrared or with VFETs, or even both, for that"s what this is all about. The circuit diagram shows an infra- red transmitter in its simplest, most elementary form. Its simplicity is achieved with the aid of a VFET. Since FETs unlike other bipolar transistors, reveal a neat linear input to output voltage ratio, it is enough to feed a low frequency signal to the gate and to include an infrared LED in the drain lead. The intensity of the infrared light produced by the LED will then vary according to that of the LF voltage put across it and there you have it — a transmitter. In order to increase the infrared LED"s lifespan, a transistor has been added to achieve current limitation, thereby reducing the FET"s maximum drain current to about 60 mA. If the current were to rise, the voltage across R2 would 5 10V VN46AF VN66AF BD 552 BD 552 1infrared transmitter F b...