Performance of the modified photodetector unit:

Performance:

- Resonant frequency f_res = 26.0MHz
- Transimpedance gain at 26MHz is 1.27kOhm (560Ohm resistance of the resonant circuit x G=4.5 x 1/2 by 50Ohm termination)
- Input referred curent noise = 9pA/rtHz
- Shotnoise intercept current is 0.24mA

Remarks:

- There is a gain peaking at 280MHz as explained in the prev elog. If one does not like this, remove 700Ohm resistor from the max4107 stage. It will increase the amplifier gain from 4.5 to 5, and the gain peaking is reduced.

- The transimpedance gain might be still too high. Then, a shunt resistor at the location of R24 can be added to the resonant circuit. This way, the shunt resistance is seen only from the RF path. Of course, lowering the signal level has to be paid by the increase of the input referred current noise level.