Infrared modulated transmitter (CB7247E)

This simple Philips circuit from the 1960s can use any general-purpose transistor. The signal is modulated at 2.7 kHz.

28 V to 5 V converter (CB7331E)
Found in National Semiconductor documentation from the 90's, this circuit has an output current of...
Transistor Characteristic Checker (CB3903E)
With this circuit it is possible to raise the characteristics of a transistor by checking its gain...
Current Transmitter for Resistive Loads (CB14316E)
The circuit presented is from the Linear Applications Handbook of the National Semiconductor of...