This circuit was found in the June 1986 issue of Radio Electronics magazine. It is based on two operational CA3140s and has a trigger voltage adjustment.
We found this circuit in a technical documentation on the National Semiconductor LM3909. The...
The LEDs act as diodes, so if good they will show the same characteristic curve. Arrangment shown...
This circuit is from an old English publication from 1968. We can implement it with TIP32...