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Need MA to voltage converter help

I have a sunlight sensor made up of 2 tiny amorphous solar cells in parallel, that I would like to use with a 0-5 volt data logger. These cells provide the spectral response I want.

The cells together generate a maximum of 2.25ma of current in full sunlight that I need to convert to voltage.

I have used a OP90 op amp in the past to do the same for other sensors, but only for microamp currents. I did the math to find the value of the feedback resistor for this, and come up with something like .0022 ohms which doesn't seem too workable. Either I am making a mistake in my math or maybe it isn't possible to do this conversion using a single op amp.

Can someone give me an option for making this a>v converter for this 2.25ma current?

Thanks Jim

Reply to
Jim
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Not sure how you came up with that resistance value, but I'd suggest you revisit your calculation. When I do it, I get 5V/.00225A =3D 2.22k ohms, not a bad value at all. Looks like you lost 6 orders of magnitude somewhere.

(It's always good to double-check your answers, especially in cases like this where the result seems odd. For example, 2.25mA times .0022 ohms is 5 microvolts, not 5 volts. In other words, plug your result back in to do the checking so you're lest apt to make the same mistake over again.)

Cheers, Tom

Reply to
Tom Bruhns

Maybe MA means Mega-Amps ?:-)

...Jim Thompson

--
| James E.Thompson, P.E.                           |    mens     |
| Analog Innovations, Inc.                         |     et      |
| Analog/Mixed-Signal ASIC\'s and Discrete Systems  |    manus    |
| Phoenix, Arizona  85048    Skype: Contacts Only  |             |
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  |
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Reply to
Jim Thompson

On Oct 9, 5:03=A0pm, Jim Thompson wrote: ...

Just solved the world's energy crunch, if so! ;-)

Reply to
Tom Bruhns 

--
View in Courier:

   
          +--[2K2]--+
          |         | 
     +----+-|-\\     | 
     |-     |  >----+-->Vout
   [PV]   +-|+/
     |    |
     +----+------------>GND
     |
    GND

JF
Reply to
John Fields

When I first read the OP, I misread it as nanoamps. ;-)

Cheers! Rich

Reply to
Rich Grise

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