I am having issues with a ‘high’ voltage level shifter I am creating. I need to drive a 28Vpp waveform with specific timings ( <.1us rise time, 1us pulse width), converting from the 3.3V logic that comes out of my microprocessor. I currently have the circuit below:
Which produces the following waveform:
Great! However, I will need to need drive a fairly long cable. When I add 100pf of capacitance to the output:
I get the following waveform:
This waveform doesn’t meet my requirements of having a rise time of less than 0.1us. What can I do to overcome this? I have tried replacing the transistor based circuit with an LM139(http://www.kynix.com/Detail/861098/LM139.html) comparator, but that was still susceptible to capacitance. Are there ICs available that could fix my issue? I can handle about 4us of prop delay if needed. Thanks!