Linear light-sensing circuit required

Hello Kryten,

AFAIK you should stay below 75% of saturation to avoid the more non-linear range. Infineon is pretty good in specsmanship even if their web site doesn't appear to be one of the best.

The 741 amp is really old. CMOS opamps aren't that expensive anymore. If it has to be rock bottom in cost you could use the LM324 with a FET in front and clamp away (auto-zero) the DC drift and offset. The 324 also comes in a thrifty low voltage version which is lean on supply current.

Regards, Joerg

Use in current mode to be linear. Just need a transimpedance amp. Basically, one op amp and one feedback resistor.

Steve J. Noll | Ventura California | The Used Equipment Dealer Directory: |

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Yes, I felt this was the better way to go

I was thinking of tying cathode to + input, anode to - input, resistor between output and - input. Also tie + input to idle voltage (as a virtual earth).

Like so:

from article

AFAICS, this ought to do it: the op-amp should pull the output voltage lower as the PD tried to force current into the - input node.

I guess this is what you meant too, and not one of those unusual transconductance op-amp thingies.

K.

On Sun, 22 May 2005 00:05:56 GMT, "Kryten" wroth:

You should have kept on Googling. Take a look at

to see something that will work right out of the box. There's a bunch of good application data in there too.

Jim

If you really mean "whiteness" you will need to use white light, not red.

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