Audio Test Amplifier (CB21044E)

This circuit was found in an old Electronics Now. The integrated circuit can be of another type with the necessary circuit alterations.

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Crystal converter (CB7327E)
This circuit was found in a Popular Electronics from the 90's. The circuit can be used to convert...
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This circuit works with only 1.5 V and can be powered by a solar panel. The circuit is from 1991....
FM transmitter for 800 m Range (CB20409E)
In fact, the original American publication exaggerated a little about the range that a good...