# Project help, need a way to allow voltage flow only if certain limit

Not sure exactly how to word this but I'll give it a shot. In my project a detector will output anything from 16uV to 750mV. To succusfully trigger a Time-to-Digital converter the voltage around the minimum of 16uV will not suffice to it needs to be amplified. I have an amplifier and comparator circuit that will achieve this, however I do not need/want it to amplify when the voltage is above 100mV. Is there anyway to set it so anything lower than 100mV will go to the amplifier and anything 100mV and above will go straight to the detector. It also needs to be in an analog way.

Basically:

If input<100mV go to amplifier then to detector

If input>100mV go to detector

If clarification is needed I'll be happy to try

Thanks!

• Are you measuring the voltage after the amplification? Or are you just running the output to a comparator (followed by a timer)? – Drew Oct 26 at 0:06
• @Drew We don't actually care what the voltage is after the amplification as long as its above 25mV. I care about the voltage coming from the detector and determining whether or not it needs to be amplified. – Dolezilek Oct 26 at 0:09
• @Dolezilek Suppose you just amplify, with clipping? Would that be fine? – jonk Oct 26 at 0:11
• @jonk I suppose it would, the main problem is the gain required to amplfify 16uV to an acceptable amount amplifies the 750mV to more than 5V which the comparator cannot take as an input. Is what you are suggesting is a way to limit the output of the amplifier? I think that would work as long as the 16uV amplification remains the same. – Dolezilek Oct 26 at 0:15
• @Dolezilek It would probably help a lot if you could present the 16 uV signal, itself, and details about how that was measured. You should also talk about the bandwidth required and the source impedance for that signal. – jonk Oct 26 at 0:59