Low battery indicator (CB9133E)

This circuit was found in Maxim's documentation from the 80's. The integrated circuit is from that time, uncommon today.

Standard 1 MHz Oscillator (CB9653E)
We found this circuit in an old American documentation. Transistors can be modern equivalents. ...
Differential Amplifier (CIR18634E)
In the figure we have the conventional configuration of a differential amplifier with the...
LM12 in Parallel Amplifier (CB14389E)
This 8 A high output power amplifier uses two National Instruments LM12s. The maximum capacity of the...