I have an impulse of ~200mV, ~50nA for about 0.15 seconds. To interface with my circuit, I need it to be 1V+. The problem is, I don't want to use an opamp, or something else that needs to be constantly powered. An ideal solution would be a relay or a FET that has a gate threshold in the millivolt range. However, I can't find anything similar to this. I have power available, but I do not want it to be used until the impulse occurs. Are there any other options for me at this low voltage level?