I have an assignment to design a transimpedance amplifier for a photodiode. The bandwidth is to be 40MHz, and there are to be two outputs, a high pass output above 20kHz and a low pass output below
20kHz all the way to DC. It is permissible that the two bands overlap a little bit.The noise performance of an amplifier is primarily determined by the noise in the first stage where it is desirable to have its gain as high as possible. I realize the first stage's transimpedance will be limited by the input current's DC output level, and if this were absent the transimpedance value could be much higher to take full advantage of the op amp's output range, and thereby have much better noise performance.
So I am wondering if it is practical to have two first stage transimpdance amplifiers, one for each output band, and between these two, and the photodiode, separate the two output bands by means of a passive LC network.
At this time I know very little about the photodiode's source impedance, and what current levels to expect.
I am aware of inductor and capacitor self resonances, and would select these passives accordingly. I have studied high frequency board layout techniques. And I know about opamp gain bandwidth constants and how to figure gain and bandwidth compromises in a op amp voltage gain circuit.