Door buzzer or alarm (CB20492E)

This solar powered circuit was found in a 1991 documentation. The transistor is a general purpose NPN.

Test Circuit for FETs (MSB065E)
The circuit in figure 1 is a dynamic test for FETs. The characteristic of a FET is displayed in...
Differentiator (CB4836E)
This is a conventional differentiator configuration with operational amplifier. In principle any...
Variable Gain Differential Amplifier (CB4927E)
Found in a Linear Technology 80s integrated circuit manual this circuit has its gain controlled from...