Phonographic Preamplifier (CB20012E)

This configuration is from the 70s, having been found in an American documentation. The transistors can be BC549 for Q1 and BC548 for Q2.

| Clique na imagem para ampliar |

Digital inverter with transistor (CB25625E)
In the figure we have the simple way to obtain a digital inverter using a general-purpose...
Two way intercom (CB20505E)
This circuit works with only 1.5 V and can be powered by a solar panel. The circuit is from 1991....
Period to voltage converter (CB8869E)
This circuit was found in a 1969 EEE. The circuit uses transistors from the era that can be...