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OP-AMP Power Supply Query
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HBates:
Hey All,
I have a question regarding the use of a single supply to an operational amplifier. My device is controlled by a Teensy 3.6 and I am planning on using a boost circuit (Figure 1) to boost the 5V pin from the Teensy to 16V and then regulate that voltage using a 12V linear regulator to ensure the supply voltage is as clean as possible.
The OP-AMP is setup as a trans-impedance amplifier for my photo-diode. As the Teensy 3.6 can only receive 3.3V MAX on the analog pins I am using a voltage divider on the output to transform the MAX 12V output to 3.3V (Figure 2). I don't want to use the 5V pin directly as I would like to get a higher measuring range from the photo-diode without saturating the detector (hence the 12V reg).
What I am wondering is whether or not what I am doing is good practice/correct or if there is a better way of getting a higher amount of measuring range from the Photodiode.
Thank you :)
EEEnthusiast:
you could use a log amp like the LOG114 with the photodiode.
http://www.ti.com/lit/ds/symlink/log114.pdf
This would boost the dynamic range by a large amount.
And it can work at 5V.
David Hess:
--- Quote from: HBates on January 30, 2020, 01:59:39 am ---What I am wondering is whether or not what I am doing is good practice/correct or if there is a better way of getting a higher amount of measuring range from the Photodiode.
--- End quote ---
There may be reasons to use a higher supply voltage but extending the measurement range is not one of them if you are just attenuating the output. Your circuit could run just as well on 5 volts, or even lower, with a suitable operational amplifier.
EEEnthusiast's suggestion to use a log amplifier to extend the dynamic range is a good one. Another way to extend the measurement range is to directly digitize the photodiode output with a wide dynamic range current-to-frequency converter.
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