• Resolved

OPA2355 to ADC: RC filter concern

I have built a 4 stage transimpedance amplifier, the first 2 stages are for gain and the last 2 for active filter. 

My signal is 1MHz with duty cycle of 50%. The active filter blocks anything above 1.5MHz (LP filter). My signal rise time is acceptable and I sample the signal using Maximum likelyhood detector approach (essentially sample when I can get the highest signal value).

The OPAMP is directly tied to ADC, there is no RC filter in between and so far I did not observe any issues, however somebody more senior suggested for me to provide an RC filter before the ADC. I am going to spin a new board and I like to ask masters if this does make sense.

The ADC I use has a 4pF capacitance with 1.5K switching resistance. The sampling time I am using is 100nSec.