NTSC bandwidth is just about 6MHz, so I want to a IC satisfying. Can you tell me exactly IC's name? And can you show me why use lowpass filter? How does it work? Thank you^^You can use an IC video amp, which are commonly available.
The filter can likely be a simple RC low-pass filter.
The comparator needs to be a high-speed IC type with a propagation delay of no more than a few ns. That's likely the most difficult part to find.
The level shifter and LED driver depends upon the LED characteristics and the LED current.
yeah, I just transmit signal in short distances. The receiver and transmitter located directly opposite each other. NTSC signal has a bandwidth of approximately 6MHz so I use 15MHz triangle wave for PWM. Is it OK? I need a IC for this job with Vin=2V. I hope you will help me. Thank you very muchWhy do you want a PWM IC at 15MHz?
The comparator generates variable width pulses but as pointed out you need high speed, high current devices to drive the LEDs.
Please expain what exactly you are trying to do, you will have great difficulty using this circuit to transmit composite video,at least with resonable quality and you also need a receiver circuit that can convert the signal back to composite before you can view it. It probably won't work with visible LEDs unless you use low brighness types and shield the light path from other light sources.