Author Topic: OP-AMP Power Supply Query  (Read 704 times)

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Offline HBatesTopic starter

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OP-AMP Power Supply Query
« on: January 30, 2020, 01:59:39 am »
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  :)
 

Offline EEEnthusiast

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Re: OP-AMP Power Supply Query
« Reply #1 on: January 30, 2020, 02:51:52 am »
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.
Making products for IOT
https://www.zscircuits.in/
 
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Offline David Hess

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Re: OP-AMP Power Supply Query
« Reply #2 on: January 31, 2020, 08:35:56 pm »
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.

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.
« Last Edit: January 31, 2020, 08:38:40 pm by David Hess »
 
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