This circuit is from an old documentation, but perfectly current. In place of the battery, 2 or 4 small cells can be used.
We found this circuit in a Popular Electronics from the 80s. The circuit is based on the LM3909, a low...
In the figure we have the basic configuration of an operational amplifier for AC signals using the...
This timer, like the previous circuits, uses a currently uncommon integrated circuit. The time is...