Non-inverting gain 30 amplifier (CB6648E)

This two-transistor circuit was found in a 1969 US documentation. Modern equivalent transistors can be used. Observe the symmetrical power supply.

Converter 12 to 28 V (CB6581E)
This circuit was found in Philips documentation from 1967. The components are of the time, being...
1800 Hz Reject Filter (CB7400E)
Found in Exar documentation from the 1980s, this circuit has a 60 dB cutoff at 1800 Hz. The...
Humidity sensor (CB25284E)
This circuit also detects IR, providing LED indication. The circuit is used to indicate humidity in...