Found in a 90s Popular Electronics, this circuit triggers a load from the audio signal applied to its input. The controlled load depends on the MOSFET.
This circuit is powered by only 3 V and can flash white LEDs from 3.2 to 3.6 V, as it includes a voltage...
This circuit with the operational amplifier CA3130 was found in an English publication from 1977....
We found this circuit in the Linear Applications Handbook of the National Semiconductor of 1994....