Hello All,
I have a prototype TIA circuit with high-gain. I have the circuit laid out on a 4-layer PCB with the input and output pins of the TIA free of any inne r-layer ground copper pours in order to reduce the parasitic capacitance be tween these pins and ground. I need the low-noise performance between 0-50k Hz out of this circuit, and in order to do this, I placed the circuit in a metal enclosure in order to shield it. What I've found is that if I don't g round the circuit to the metal box, I get noise peaking at frequencies high er than 20kHz. Grounding the circuit to the box eliminates this peaking.
This circuit will be part of a bigger circuit, so I was planning on includi ng a guard-ring in the layout that would surround this TIA circuit that I w ould solder on a metal can that would act like the metal box I used for my prototype. I was wondering if anyone had knew of any "shields" that I could purchase somewhere that would accomplish this, or if anyone had any layout suggestions that could possibly mitigate this noise issue?