Hardware Description
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3.5.2
External Feedback Resistor
The TIDM-TIA also has an option to use an external feedback resistor for a different voltage gain.
Figure 3
shows the functionality of jumpers JP3 and JP4 with regards to selecting a feedback resistor.
Figure 3. Feedback Resistor Jumpers
By default, there is a jumper connecting the
Int
and middle pins of JP3 and JP4 to use the onboard
feedback resistor. Connecting the
Ext
and middle pins of both JP3 and JP4 allows for the use of an
external feedback resistor. An external resistor can be connected to the TIDM-TIA board by blue-wiring a
resistor to the R4 location on the board at the two holes. Knowing a target output voltage and measuring
the current from the photodiode makes it possible to use
Equation 1
to select a proper feedback resistor.
4
MSP430F2274 Transimpedance Amplifier (TIDM-TIA) User's Guide
TIDU443 – August 2014
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