Hello
There are already a lot of topics about transimpedance amplifier with a lot of references and I'm now waiting for the Graeme's book about photodiode amplifier. But there is one issue that is not so discussed : the bias voltage.
I'm using a custom bidimensional PSD with 2 anodes and 2 cathodes. The typ. value of the resistance between 1 anode and 1 cathode is 150 Ohm (which is very very low compared to photodiode resistance : 100meg or giga ohms) the capacitance between 1 anode and 1 cathode is 1,5 nF (which is also very big). The output current is about 100=B5 amp and its bandwidth is around 4 MHz.
I decided to use the OPA657 for my transimpedance amplifier. I have a feed back resistor of 1.8K with a parallel capacitance of 12 pf. This configuration gives me not so bad results : ~3 MHz bandwidth (simulated with PSpice). But my problem is that by addind a bias voltage of few volts on the non inverting input, both simulation and real measurements showed a reduced bandwidth to ~100kHz. I think this is due to the small detector resistance but I'm not so experienced to say more about.... Any ideas ? by the way the max positiv voltage of the opa657 is 2,5V, do you know similar product that could achieve a bias around 10 or 15 V ?
Thanks you electronicians!