Found in an English publication from the 1980s, this circuit can be built with equivalent transistors such as the BC549. The signal must be applied to an external amplifier.
This CMOS circuit with the 4011 can be used in an infrared remote control. The circuit can be...
This circuit was suggested by Popular Elecronics from the 90's. The circuit has high input...
This circuit has a high input impedance and uses two transistors quite common in the market. Its...