THORLABS DET100A User Manual page 12

Si Biased Detector
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 held at zero volts across the
photodiode, since point A is held at the same potential as point B by the
operational amplifier. This eliminates the possibility of dark current.
•
Photoconductive mode: The photodiode is reversed biased, thus
improving the bandwidth while lowering the junction capacitance. The
gain of the detector is dependent on the feedback element (R
bandwidth of the detector can be calculated using the following:
where GBP is the amplifier gain bandwidth product and C
the junction
capacitance.
Page 11
( −3 ) =
capacitance, amplifier
,
4 ×
capacitance,
is the sum of
D
and feedback
Rev F, December 8, 2014
). The
F