Hi I am designing a transimpedance amp that is supposed to be 400M gain, 10kHz bandwidth and 800 micro volt RMS noise on the output. I am using a single OPA354 opamp with 100M RF and 30k/10k Tee network to give a total gain of 400M. The problem that I have is that the noise level is too high (3mV RMS) once the photodiode is in circuit - presumably from the capacitance giving noise gain. The capacitance is high as I currently have no bias applied to the photodiode as this will cause leakage and shot noise, particularly at high temperatures.
Does anyone have any advice on getting the noise level down? Is the noise that I am seeing simply an amplification of the opamp input voltage noise caused by the photodiode capacitance?
Thanks
Mike Price