I have an application to detect flames using ionisation probes. Probes are constructed of a stainless steel coaxial cable. It is then biased with 80Vdc and as the flame reach the probe, I can achieve a pulse due to micro amp level current flow in the circuit (conduction occur through coaxial cable due to ions in flame). Following is the circuit that I am using at the moment which works fine for just one probe. However as I need 12 such probes and use a common supply, I observe cross talk between them.
So, I think I need to change my amplification circuit. The output of the amplifier triggers a digital input of an FPGA to log data in PC. therefore I need the amplifier designed to produce a TTL pulse as it detects the micro amp level current flow in the ionisation probe circuit.
I have used open loop configuration to achieve the maximum gain.
Really appreciate if you can advise me on this - particularly to design the amplification circuit.
what is Y1 in your schematic. I do not follow exactly what you are doing but you can look at figure 36 of OP77 datasheet hwich gives you detection and amplification. You may need to do adjustment for your needs.