=== Photodiode as current source === \\ \\ \\ {{drawio>lab05:Fig-120_inverting_op-amp_photo_diode_housing.svg}}\\ \\ \\ \\ \\ {{drawio>lab05:Fig-110_inverting_op-amp_photo_diode_diagramms.svg}}\\ \\ \\ \\ \\ {{drawio>lab05:Fig-100_inverting_op-amp_photo_diode.svg}}\\ \\ \\ \\ $U_{\rm DD}{\rm~=10~V},~U_{\rm SS}{\rm~=-10~V}$\\ \\ \\ We are assuming a well-lit room with an illuminance of 300 lx, lit by a white LED. White light is a mixture of many wavelengths across the visible spectrum, roughly 380 to 780 nm.\\ For a typical white LED, the spectrum usually comes from a blue LED chip with a peak around 450 nm, plus a broader phosphor emission that spreads across green, yellow, and red wavelengths.\\ For an easier calculation, we take a mean value of 500 nm which is close to the peak value of the blue LED and 300 lx for the illumination. (500 nm is in reality a greenish light and not blue)\\ The graph in shows that the photodiode sensitivity at 500 nm is only 30%. The maximim current (100%) at 300 lx is 30 ${\rm\mu}$A.\\ We can now estimate the current we would expect from the photodiode at 300 lx:\\ \\ $I_{\rm 1} = 30 {\rm~\mu A} * 0.3 = 9 {\rm~\mu A}$\\ $I_{\rm 1} \approx 10 {\rm~\mu A}$\\ \\ 30% of 30 ${\rm\mu A}$ is roughly 10 ${\rm\mu A}$.\\ **We will assume a current of 10 ${\rm\mu A}$ at 300 lx for our calculations.**\\ \\ Complete the arrows in the circuit diagram in .\\ Calculate ${\rm R_2}$ so that $U_{\rm OUT}$ = 5 V at 300 lx. Take a resistor from the E6 series that is as close as possible to the calculated value.\\ Also enter the values for $I_{\rm 1}$, $I_{\rm 2}$, $U_{\rm 2}$ and $U_{\rm OUT}$.\\ \\ \\ $I_{\rm 1}{\rm~=}$\\ \\ \\ $I_{\rm 2}{\rm~=}$\\ \\ \\ $U_{\rm 2}{\rm~=}$\\ \\ \\ $U_{\rm OUT}{\rm~=}$\\ \\ \\ \\ \\ \\ \\ \\ \\ \\ \\ \\ \\ \\ \\ \\ \\ \\ \\ \\ \\ $R_{\rm 2}{\rm~=}$\\ \\ \\ \\ What value would you expect for $U_{\rm D}$ in and why?\\ \\ \\ $U_{\rm D}{\rm~=}$\\ \\ \\ ${\rm ................................................................................................}$\\ \\ ${\rm ................................................................................................}$\\ \\ ${\rm ................................................................................................}$\\ \\ ${\rm ................................................................................................}$\\ \\ ${\rm ................................................................................................}$\\ \\ ${\rm ................................................................................................}$\\ \\ \\ \\ What value would you expect for $U_{\rm D}$ at 300 lx when the photodiode is not connected to the Op-Amp or any other electronic component (open-circuit voltage) and why?\\ \\ \\ $U_{\rm D}{\rm~=}$\\ \\ \\ ${\rm ................................................................................................}$\\ \\ ${\rm ................................................................................................}$\\ \\ ${\rm ................................................................................................}$\\ \\ ${\rm ................................................................................................}$\\ \\ ${\rm ................................................................................................}$\\ \\ ${\rm ................................................................................................}$\\ \\ \\ \\ \\ Measure or calculate the values given in the table below. \\ \\ {{drawio>lab05:Table-1_inverting_op-amp_photo_diode.svg}}\\