DET08CFC(/M)
Page 11
Rev B, April 29, 2015
One can also use a photodetector with an amplifier for the purpose of achieving
high gain. The user can choose whether to operate in Photovoltaic of
Photoconductive modes. There are a few benefits of choosing this active circuit:
•
Photovoltaic Mode:
The circuit is maintained at zero volts across the
photodiode, holding point A at the same potential as point B by the
operational amplifier. This eliminates the possibility of dark current.
•
Photoconductive Mode:
The photodiode is reverse biased improving
the bandwidth while lowering the junction capacitance. The gain of the
detector is dependent on the feedback element (R
F
). The bandwidth of
the detector can be calculated using the following equation:
(−3
=
4
×
,
Where GBP is the amplifier product gain-bandwidth and C
D
is the sum
of the junction capacitance, amplifier capacitance, and feedback
capacitance.
