Voltage amplifier with the 37 tube (T392E)

Found in a modern design book with tubes, this stage with the triode 37 has a plate current of 3.7 mA.

Noise generator with amplification (CB9931E)
Found in a Motorola documentation from the 70s, this circuit makes use of transistors of the time....
12 to 3 V x 1 A Reducer (CB4844E)
In the figure we show how to use common diodes to get a reference near 3 V in a car gearbox. The...
Ultra Low Ripple 12V Power Supply (CB9507E)
The transistors of this 12 V x 150 mA power source can be BC558 for PNP and BD135 for NPN. The...