Hello kind people! I want to represent the light falling on a photodiode as the voltage across a resistor and then amplify that voltage such that the minimum is between 0-1V and the maximum is between 4-5V. This then gets fed into an ADC.

http://harryysherwood.files.wordpress.com/2013/09/schemeit-project.png

The individual blocks of the above circuit appear to work fine, but my problem has been connecting the first (transistor) to the second (741 op-amp). Does anybody have any advice for how these two should be connected so that I can achieve what I need to? I am also aware that there may be other mistakes in how I've wired up my op-amp, so do let me know if the middle bit needs re-designing!

Thank you so much!

 

You can't feed the input of a 741 with any voltage that is closer than 3 volts to the power supply voltage. A 741 with a 5V supply is useless. Pick a different amplifier chip or give the 741 +/- 15 volts to work with.

Besides that, the voltage at R4 is never going to cross the 5 volt input. This circuit is just wrong. First guess? Make an adjustable threshold voltage for the non-inverting input.

Partial answer. Have to go to work now.

 

Do yourself a favor: look up <photodiode transimpedance amplifier> and work from the designs you find. And yes, select an amplifier that works on the voltage you intend to use!