Found in Exar documentation from the 1980s, this circuit has a 60 dB cutoff at 1800 Hz. The circuit can be adapted to operate at other frequencies.
The purpose of this circuit is to match two operational amplifiers that operate with different...
This low current circuit is suitable for powering the previous circuit and other strobe lamp...
The LEDs act as diodes, so if good they will show the same characteristic curve. Arrangment shown...