Photovoltaic-mode Cut-Off frequency

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Hi guys

I have a question about the understanding of Photodetector in photovoltaic-mode and their cut-off frequency. The frequence limited by the capacity of the Photodiode (example a PiN) and by the size of the load impedance.
So it is possible to have a cut-off frequency at some MHz? In the most Applicationsnodes, they talk about 200-350 kHz. Is there something i forget, for example to take account of the carrier transport in the semiconductor?

Regards,
Tim
 

For high speed operation they usually reverse bias the junction which decreases the junction capacitance, greatly improving speed, but the noise increases.
Running in p-voltaic mode into a low impedance load, gets the speed up but at expense of low sensitivity.
The device running into a low impedance load,can be modelled as the junction capacitance in series with a small series resistance running into the load resistance. So BW is limited by the TC of load plus series resistance and the junction capacitance.
So there is an assymtotic ultimate BW limit set by the time constant of the junction capacitance and the series resistance of the particular device, as the load tends to zero.
 
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