I made a digital input circuit to convert a 120Vac waveform into a digital 2.3V signal. I would like to add a "low-pass" filter at the output to get a low level for higher frequencies than 1kHz. I can't just use an inverter after a classic low-pass filter because I need to keep the high-low sequence for frequencies below 1kHz.
All suggestions are welcome
What I want below the cutoff frequency :
What I want above the cutoff frequency :
As you know, a low-pass filter will "smooth" v(OUT) until it becomes a 2.3V DC, and that's what I want to avoid. I want my digital input to be inactive for high frequencies.