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Questions tagged [photodiode]

A photodiode converts light to an electric current.

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61 views

Photodiode to detect light

For a university purpose I am preparing a project, actually I am thinking of using a photodiode in reverse bias in order to measure intensity of light. I divided this project in some phases: 1) ...
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1answer
65 views

Photodiode - circuit questions

I am a bit confused on a few things regarding photodiodes. Here are two circuits that I am referring to: or   For the second circuit the capacitor is not of importance. Here are my fundamental ...
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58 views

Do photodiodes break KVL?

I know what you are thinking, but hear me out. Let's do KVL in this loop: simulate this circuit – Schematic created using CircuitLab We get: $$ -V_{PD}+I(R_s+R_L)-V_1 = 0 $$ Now we solve for ...
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24 views

What is the voltage across a photodiode bellow the Saturation Limit?

This is the equivalent circuit for a real photodiode: simulate this circuit – Schematic created using CircuitLab Source. I added a Bias Voltage based on Figure 1-9 (a) of the Opto-...
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1answer
53 views

How much slower does a photodiode become in photovoltaic mode?

Take for example this photodiode, the main differences between using it in photovoltaic and photoconductive mode is the rise time and the Dark Current, aren't they?. I know exactly how the Dark ...
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1answer
40 views

How does the spectral response of a photodiode change with bias voltage?

Look at this data sheet, in the second page we have a graph for the spectral response. Now, I have learned that photodiodes must be reverse-biased in order to get a decent signal from them, but then ...
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35 views

How much does the Bias Voltage affect the NEP of a photodiode?

Look at this data sheet for example. Everything there is measured at 0V, including the NEP, if I connect that photodiode in reverse bias, how will that NEP change?. I'm inclined to believe that it ...
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1answer
44 views

In this semi-ideal photodiode, what would be the physical interpretation of this current?

A real photodiode can be expressed as a circuit made of several ideal components, it looks something like this: simulate this circuit – Schematic created using CircuitLab I copied it from here ...
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1answer
139 views

PCB design review: analog routing

I am designing a PCB with analog signals for the first time, and I would really appreciate any feedback on my layout and routing. The circuit is a light-meter, consisting of a photodiode connected ...
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3answers
2k views

Why are “square law” devices important?

In the literature, I often see the notion of square law devices. Why are these devices important, to the extent that they have their own characterization as square law device? In what context does ...
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1answer
96 views

how does single supply op-amp work while its non-inverting input is connected to ground?

In HCNR200 Datasheet, the page 11, figure 13-A, there is a sample that confused me. In this sample, the Vin is applied to the inverting input and if the electric current passes through PD1, PD1 ...
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1answer
42 views

Photodiode current equation

The current in photo diode because of generation rate G and depletion width W is given as qGW (neglecting diffusion currents). When the light is incident on the diode excess carriers are generated in ...
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62 views

PCB dual LED emitter, TIA and voltage regulator (beginner)

Does this PCB look good for this operation? The schematic is attached. I have a voltage regulator connectected to an LED emitter. Voltage regulator to TIA . TIA then is attached to active high pass ...
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2answers
42 views

Driving Avalanche Photodiodes (PCBs)

I am using Avalanche Photodiodes and I was told that they use a much higher voltage then standard photodiodes and I was wondering if I need a High Voltage PCB to drive them? I am currently just using ...
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2answers
69 views

Photodiode Output measurement

I'm using Hamamatshu s8559 photodiode to convert x-rays into it's respective energy. I'm using a 10 bit ADC converter. The problem I'm facing is I have no relationship between the Photo-current ...
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2answers
97 views

Very low current (<10 microamps) darkness detector circuit that turns off in light

I've made a device that lights an LED at a very low current (<10 microamps) as a very dim indicator for use in the dark. At its simplest, the circuit is a 3V coin battery + resistor (300K-1M ...
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1answer
50 views

How to use my bits to transmit this photodiode signal in the most efficient way possible? [closed]

Suppose I have photodiode with a Dark Current of 5 pA and that using the NEP of that photodiode at some frequency \$\lambda\$ I determined that the smallest signal I could detect was of 1 pA. First ...
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1answer
22 views

Phototransistor and Photodiodes capacitances when some in an array sense light

I'm using phototransistors to sense low speed data (about 7 bits a second). With one phototransistor and a 300K resistor, I found my sweet spot and can transmit correct data with lazer. I find if the ...
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1answer
150 views

Can you connect multiple photodiodes in parallel and treat it as one?

Im working on an IR sensor based off of the Texas Instr. particle sensor (TIDA-00378). They use just one photodiode in their design. I would like to use multiple photodiodes, lined up with multiple ...
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1answer
38 views

making a photodiode module

I am trying to do stimulated Raman scattering microscopy. In this experiment two pulsed laser beams are used . The wavelength of these two laser beams is tuned to match a specific Raman frequency of ...
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1answer
58 views

Why isn't the Saturation Current of a Photodiode the same as its Short Circuit Current?

The formula I see everywhere is: $$ I_{sat} = \frac{V_{bias}}{R_L} $$ But this seems incomplete for the following reason: The larger the resistance is the smaller the Saturation Current, it stands ...
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5answers
143 views

Please explain this formula for the relationship between bandwidth and the temporal response of a photodetector

I am reading "Optoelectronic Sensors" by Didier Decoster and Joseph Harari. At section 1.8.2 they start explaining the relationship between rise time and bandwidth, and they give a very weird formula ...
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3answers
962 views

Forward drop of diode vs forward drop of LED

It is always said that forward voltage drop in the diode is around 0.7 volts. LED also being a diode, why does it have a greater forward voltage drop of around 3 Volts? What is the model of LED that ...
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1answer
52 views

LED output with Photodiode and Function Generator

Some of my student and I are designing a Physics experiment involving a high power LED, a square wave from function generator (50 ohm output impedance) and a digital oscilloscope (1 MOhm imput ...
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49 views

How to calculate the current produced by a solar panel?

The equation for calculating current when given voltage and temperature is known as the 5-Parameter model ie. \$I = I_{ph} - I_o[\exp(\frac{V + R_sI}{nV_t})-1] - (\frac{V+R_sI}{R_{sh}})\$ Since this ...
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1answer
67 views

How does a camera pixel accumulate charge (colour)?

I refer to the Wikipedia entry for a CMOS camera sensor's individual pixel. There is a schematic like so:- and a statement that:- The read-out transistor, Msf, acts as a buffer (specifically, a ...
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1answer
43 views

Explanation of 5 Parameter Model for Solar Cells

I am having a hard time understanding this equation, the 5 Parameter model for photovoltaic cells. \$I = I_{ph} - I_o[\exp(\frac{V + R_sI}{nV_t})-1] - (\frac{V+R_sI}{R_{sh}})\$ My goal is to apply a ...
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0answers
60 views

Estimate minimum detectable light pulse in a photodiode (5 ms, 44 kHz modulated)?

I'll use an IR LED modulated at 44 kHz to illuminate particles in air or water, and will use a silicon photodiode to detect weak pulses of scattered light as they pass through the LED's collimated ...
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1answer
29 views

Output changes wildly with input voltage in photodiode circuit

I am currently analyzing a photodiode sensor input circuit (not designed by me, but schematics drawn from a commercial product). I am currently simulating the circuit on TINA TI. While experimenting ...
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2answers
30 views

How will the resistance of this Evaluation Module affect the measurements of the current produced by this photodiode?

A little context: This is part of a bigger project about glowing algae, my job is to design a photodiode array to measure the amount of light the algae produce in response to movement. I have a good ...
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1answer
65 views

How does this op-amp photodiode circuit behave?

I am trying to understand the inner workings of a photoelectric object sensor I have in my hands. (modulated with 24 kHz) Here is the very beginning of the receiver part: simulate this circuit –...
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85 views

Making LED flash from steady-state signal

I am looking to design a simple circuit that detect objects placed in a spot. So far, the circuit uses simple IR LED and photodiode to detect the object placed between them. The voltage developed in ...
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1answer
34 views

Resistor on transimpedance amplifier input?

I am currently examining an expired patent file of a photoelectric sensor. The file includes the circuit, I am trying to understand it with my limited analog electronics knowledge: Patent no: ...
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0answers
120 views

PV cells (photovoltaic) I-V curve plot simulation

I am trying to plot the I-V curve using python because that helps me in understanding PV cells / solar panels (and diodes as a general thing). I know the formulas ...
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1answer
17 views

How to properly use an OPB917BOCZ photoswitch?

I am building a weather station with an anemometer. I have an OPB917BOCZ photoswitch on-hand that I would like to use as the tachometer if possible. However, I can't seem to have any luck with it. ...
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1answer
68 views

How to connect a 2 pin photodiode?

Initially, I have used 3 pin photodiodes, where the anode is connected to the resistor and has a wire which goes to group and the other goes to an analogue input to read the voltage. The cathode is ...
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3answers
105 views

Correct use of op-amp to amplify photodiode in reverse bias

So I have a photodiode in reverse bias, from which I intend to measure my pulse. Currently, my schematic looks as follows: simulate this circuit – Schematic created using CircuitLab Weirdly,...
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4answers
822 views

How to tell how sensitive a photodiode is?

I am looking to buy some new photodiodes for a project. Currently, I have been using expensive photodiodes with a picosecond level rise and fall time and a very small area to pick up light. The ...
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4answers
532 views

Photodiode almost no mV at analog port

So I have bought a photodiode, which I intend to hook up to the analog port of my Arduino, so that I can measure differences in the light that the photodiode picks up. I realized, that when I don't ...
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1answer
64 views

High speed photodiode for laser pulse width measurement

I want to measure the temporal width of a Q-Switched laser (which should be close to 5 ns) and the delay between two lasers that I send in my experiment. The delay is between 1 ns and 1 µs. Wavelength ...
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1answer
41 views

where do i find max short circuit current of photodiode?

I'm trying to convert the current signal from a photodiode to voltage through a transimpedence amplifier. The photodiode is put in photovoltaic mode in order to get the greatest accuracy and lowest ...
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1answer
53 views

Schematics of PIN Photodiode interfacing with an ADC

This question is in continuation of my previous question. I am moving forward with PCB designing now. I have selected low input-bias current op-amp AD8616 for converting current signal into voltage. ...
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1answer
136 views

Laser Microphone setup

I am currently constructing a laser microphone using 5mW red laser pointer source based on the idea below, not directly output to a speakers or headphones, but the signals must be fed into computer ...
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1answer
38 views

The breakdown voltage of APDs

what does the breakdown voltage of an APD tell me? I know certain methods how to determine it but, what happens after reaching that point? More specific: Is the gain afterwards constant or still ...
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1answer
114 views

Why is this photodiode operated in reverse bias

Referring to the following document by NXP on figure 9. The cathode of a given photodiode is connected to the transimpedance amplifier in forward bias. To me, this seems wrong, as almost every ...
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2answers
78 views

Better resolution with photodiode (LTR-536AD)

I want to build something like a fog-sensor. I'm using a laser and on the other end (~20m) I have a LTR-536AD photodiode. I hooked the photodiode to an arduino and was monitoring the voltage. My ...
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1answer
95 views

Correct use of transimpedance amp

So I realized that it might become a necessity for me to use a transimpedance amplifier for a pulse watch that I intend to make. Some background: The pulse watch shoots light at 940 and 660nm at ...
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1answer
58 views

Does this photodiode need an operational amplifier?

I'm trying to make a circuit for a pulse watch, which should be capable of measuring blood SpO2. I use 2 LEDs for each wavelength (respectively 660nm and 940nm) to shine at the upper wrist. The ...
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1answer
119 views

Photodiode temperature compensation

The goal is to design a circuit that can accurately measure light intensity with little temperature dependency. Common application uses photodiodes to do so. Photodiodes can be measured either in ...
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1answer
204 views

Arduino breakout schematic for FDS100 Photodiode

This is the first time I'm drawing a schematic, thus why this question seeks to get clarification from you experienced engineers :-) A little background information: I'm trying to draw a circuit ...