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lab05_en:inverting_op-amp_photo_diode_as_current_source [2026/04/14 09:53] – [Photo Diode as current source] mexleadminlab05_en:inverting_op-amp_photo_diode_as_current_source [2026/04/28 16:13] (current) – mexleadmin
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-=== Photo Diode as current source ===+=== Photodiode as current source ===
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-{{drawio>lab05:Fig-110_inverting_op-amp_photo_diode_diagramms.svg}}+{{drawio>lab05:Fig-120_inverting_op-amp_photo_diode_housing.svg}}\\
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 +<imgcaption Fig-120_inverting_op-amp_photo_diode_housing | Inverting Op-Amp: Photodiode BPW 34 S> </imgcaption>\\
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-<imgcaption Fig-110_inverting_op-amp_photo_diode_diagramms | Inverting Op-Amp: Photo Diode as current source> </imgcaption> 
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 +{{drawio>lab05:Fig-110_inverting_op-amp_photo_diode_diagramms.svg}}\\
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 +<imgcaption Fig-110_inverting_op-amp_photo_diode_diagramms | Inverting Op-Amp: Diagramms of BPW 34 S> </imgcaption>\\
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-{{drawio>lab05:Fig-100_inverting_op-amp_photo_diode.svg}} 
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-<imgcaption Fig-100_inverting_op-amp_photo_diode | Inverting Op-Amp: Photo Diode as current source> </imgcaption> 
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-$U_{\rm DD}{\rm~=10~V},~U_{\rm SS}{\rm~=-10~V}$\\ \\ 
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 +{{drawio>lab05:Fig-100_inverting_op-amp_photo_diode.svg}}\\
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 +<imgcaption Fig-100_inverting_op-amp_photo_diode | Inverting Op-Amp: Photo Diode as current source> </imgcaption>\\
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-Complete the arrows in the scematic of the circuit.\\ +$U_{\rm DD}{\rm~=10~V},~U_{\rm SS}{\rm~=-10~V}$\\
-Take the values for $U_{\rm 1},~U_{\rm 2},~U_{\rm OUT}$ from <imgref Fig-30_inverting_op-amp_inv_input>.\\ +
-Use these values to calculate the sum of the voltages at node ${\rm N_{12}}$.\\ +
-Compare your result by measuerement.+
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 +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 <imgref Fig-110_inverting_op-amp_photo_diode_diagramms> 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:\\
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-$U_{\rm 1}{\rm~=}$+$I_{\rm 1} = 30 {\rm~\mu A} * 0.3 = 9 {\rm~\mu A}$\\ 
 +$I_{\rm 1} \approx 10 {\rm~\mu A}$\\
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 +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.**\\
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 +Complete the arrows in the circuit diagram in <imgref Fig-100_inverting_op-amp_photo_diode>.\\
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-$U_{\rm 2}{\rm~=}$+Calculate $R_{\rm 2}$ 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 $U_{\rm OUT}$.\\
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-$U_{\rm OUT}{\rm~=}$+\\ 
 +$I_{\rm 1}{\rm~=}$\\ 
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 +$I_{\rm 2}{\rm~=}$\\ 
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 +$U_{\rm 2}{\rm~=}$\\ 
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 +$U_{\rm OUT}{\rm~=}$\\ 
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 +$R_{\rm 2}{\rm~=}$\\ 
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 +What value would you expect for $U_{\rm D}$ in <imgref Fig-100_inverting_op-amp_photo_diode> and why?\\ 
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 +$U_{\rm D}{\rm~=}$\\ 
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 +${\rm ................................................................................................}$\\ 
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 +${\rm ................................................................................................}$\\ 
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 +${\rm ................................................................................................}$\\ 
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 +${\rm ................................................................................................}$\\ 
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 +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?\\ 
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 +$U_{\rm D}{\rm~=}$\\ 
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 +${\rm ................................................................................................}$\\ 
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 +${\rm ................................................................................................}$\\ 
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 +Measure or calculate the values given in the table below. 
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 +{{drawio>lab05:Table-1_inverting_op-amp_photo_diode.svg}}\\ 
 +<tabcaption lab05:Table-1_inverting_op-amp_photo_diode | Photodiode measured and calculated values> </tabcaption>\\ 
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-Calculated $U_{\rm 12}{\rm~=}$ 
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-Measured $U_{\rm 12}{\rm~=}$ 
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-What are your results?\\ 
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-What will happen if you short-circuit $R_{\rm 2}$?\\ 
-Try it and explain your results.\\ 
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