This basic Schmitt trigger was found in an American publication from 1968. The circuit uses transistors from the time. Modern general-purpose types can be used.
This source is used to supply circuits with operational amplifiers, being originally created for...
The transistors in this 80's documentation project may be BC548, the most modern equivalents of...
This circuit uses a FET to drive an LED with constante currente. The current up to 20 mA can be...