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Hi everybody,
I am an engineering student working on a relative simple project: I need to measure the current generated in a photodiode (several of them actually but does not matter) stimulated by a LED.
The application requires a low bandwidth (no more than a few Hz) but high accuracy and...
Well, I started with a TIA coupled with a microcontroller ADC.
However I needed higher resolution and a wider dynamic range at low cost, while speed was not important. Furthermore I was interested in signal integration (charge), but over long period of time (no charge sensitive amplifier).
I had...
I can't; in fact I start to believe is just normal. This is a simple application and i cant find any weirdness. Anyway, I checked the inverting pin voltage and I saw a small forward bias during the transient, so adding a small reverse bias was a good suggestion. I'll leave the circuit in this...
Well, today I put a reverse bias across the photodiode. Unfortunately the drift was still there. Sometimes positive sometimes negative. I am a bit lost. Anyway thank for suggestion.
Actually I put a voltage offset compensation network on the n.i. op amp input (+-500uV). I'll try with a larger bias.
Anyway I checked the inverting input voltage several times, and I did not see any transient positive bias (the transient reverse bias is maximum 5mV then drops to zero).
Just to...
Hi all,
I designed a discrete light to frequency converter using a LM331 in a "precision voltage to frequency converter" configuration.
I attached the schematics. This circuit works well when I use a controlled voltage (and a resistor) or a current source as the input, but when I put the...
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