What is Photodiode: Definition and 72 Discussions

A photodiode is a semiconductor p-n junction device that converts light into an electrical current. The current is generated when photons are absorbed in the photodiode. Photodiodes may contain optical filters, built-in lenses, and may have large or small surface areas. Photodiodes usually have a slower response time as their surface area increases. The common, traditional solar cell used to generate electric solar power is a large area photodiode.
Photodiodes are similar to regular semiconductor diodes except that they may be either exposed (to detect vacuum UV or X-rays) or packaged with a window or optical fiber connection to allow light to reach the sensitive part of the device. Many diodes designed for use specially as a photodiode use a PIN junction rather than a p–n junction, to increase the speed of response. A photodiode is designed to operate in reverse bias.

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  1. kplee

    DC blocking the photodiode signal

    Hi all, I was trying to detect small optical signal through amplification process and realized that there is a huge DC background behind the AC signal. So I decided to remove the background using a Thorlabs DC blocker (EF500). The photodiode I used was Newport 818-bb-21, and the signal before...
  2. klismann

    Please help me with this quetion about an Avalanche Photodiode (APD)

    [Moderator's note: Thread moved from a non-homework forum and thus lacks the homework template] Summary:: It is a small question that my teacher gave me about avalanche diode. Anyone who can help me will be very grateful. Consider an avalanche photodiode of InGaAs, which operates at the...
  3. louisnach

    Obtaining the series and shunt resistance of a photodiode from the datasheet

    Hello, Hello, For a project , i need to modele a photodiode with a current source in paralelle with a shunt resistance and in serie with a resistance to use it in a bigger circuit. The photodiode we will use is SFH7050, the datashhet is provideed here...
  4. K

    Photodiode: pulsed vs. continous signal

    Hello, I have done an experiment with cutting out a pulse from continuous laser using Pockels cell. The setup is cw laser -> Pockels cell with crossed polariazers -> photodiode. The photodiode is connected in reverse bias, a capacitor is connected parallel to photodiode. If I put a half wave...
  5. F

    Poisson distribution and Shot Noise

    My setup: I have the an LED (LED370E) in front of a photodiode (S12915-16R). The photodiode is connected to an ADC (DT5751) which has a counting functionality. The way it works is that it counts how many times the signal goes above a certain threshold and makes a histogram out of it. I know...
  6. F

    Solving the Debate Over Photon Counting With a Scintillation Device

    Hello, I'm working on a scintillation device to detect protons, I have a disagreement with one professor and I would like your opinion. There is one photodiode model we want to use to measure the light intensity from the scintillators, and we want to relate the signal of that photodiode with...
  7. S

    Are there photodiode fabs that give the P and N length scales?

    I am interested in purchasing Si, GaAs and/or Ge PN and PIN photodiodes, where the manufacturer would also supply the length scales as well as the doping, of the P, I and N layers. Commercial suppliers don't reveal this information [moderator: solicitation removed.]
  8. D

    PIN photodiode forward bias capacitance

    Hello! I've done tons of research on a problem and can't seem to figure something out. I'm looking at operating a photovoltaic PIN photodiode. Since it's operating in photovoltaic mode, it will produce a current when light hits it, and this will produce a forward voltage. I've researched...
  9. M

    Photodiode - circuit questions

    I am a bit confused on a few things regarding photodiodes. Here is are two circuits that I am referring to: or For the second circuit the capacitor is not of importance. Here are my fundamental questions: 1. Why do we need an external voltage? 2. Why do we need a resistor? 3. What is...
  10. Jalo

    I Photodiode bandwidth: why does power decrease with frequency

    Hi, I'm studying p-i-n photodiode (PD) at the moment and understand that the photodiode's response will depend on the frequency of the light signal going into it. I am struggling however to understand the concept of bandwidth, and why is it that the photocurrent at the PD decreases with higher...
  11. Phantoful

    Voltage on a quadrant photodiode used with an AFM

    Homework Statement An AFM uses a quadrant photo-diode to measure the deflection of the laser beam. Sketch the voltage in quadrants A, B, C and D as the tip travels on top of a single carbon nano-tube resting on a flat surface when the AFM is operating on tapping mode. Homework Equations Not...
  12. D

    Quadrant photodiode selection advice

    Hi all, I have a post related to this question over in the 'general engineering' forum located here: https://www.physicsforums.com/threads/beam-centering-using-a-photodiode.926814/#post-5854037 However, my question is a little more specific hence the new thread. I need to select an...
  13. D

    Beam centering using a photodiode

    Hi all, I am a mechanical engineer so I'm hoping to get a bit of guidance on something I am working on at the moment. I am working on a project which requires we keep actively keep a laser beam centered on a mirror. The mirror transfers a small percentage of beam power and I am hoping to use a...
  14. Telemachus

    Photodiode for light detection

    Hi. I am willing to make an experiment with light. The idea is to have a light source (specifically a led light) and a photodiode to detect the light and make some spectroscopy. The photodiode has to detect the light in the same frequency that is emitted by the led. I'm not an expert in...
  15. S

    Voltage output of a photodiode (solar cell)

    Hi, I'm trying to figure out how the angle of incidence will affect the voltage output of a photodiode. The obvious answer that comes to my mind is that the voltage output should be proportional to the cos(α), where α is the angle of incidence of light. However, I couldn't find any...
  16. H

    Using a photodiode in optical communications

    Homework Statement [/B] As part of my coursework in a sensor systems module at university I was given the question: State the most important reason why the photovoltaic (as opposed to photoconductive) mode would be the most suitable choice for a long distance fibre optic transmission system...
  17. Irfan Nafi

    Difference between reverse bias and forward bias for a photodiode

    I'm creating a project where the motors have to be triggered by a photodiode. A light provides a steady stream of current to the photodiode and when that incident light is scattered, the motors move. But in reverse bias a photodiode needs to have a dark environment to provide 'infinite...
  18. S

    Point source of light, opaque screen with hole. photodiode problem

    Homework Statement A point source of light (wavelength \lambda = 600 \, \text{nm} ) is located a distance x = 10\,\text{m} away from an opaque screen with a small circular hole of radius b. A very small photodiode is moved on an axis from very far away toward the screen. The first...
  19. S

    Measuring Pulsing Current Output Average From Photodiode

    Hello all, I will be using a photodiode to measure optical power. The photodiode will convert this power into a current. The optical power will pulse rapidly in 15 ns periods with a 5 ns on-time (at full amplitude) and a 1 ns rise and fall time. I am looking for an analog averaging solution...
  20. A

    Photodiode parallel to a capacitor

    Dear Forum Members, I am looking for someone who can help me to model the behavior of a photodiode in parallel with a capacitor. I want to model the behavior of a device that I have developed. As you can see in my attached file, the photodiode shows a current-to voltage characteristic with a...
  21. M

    Amplifying a Photodiode using an OpAmp

    Dear electrical engineers, Here a question from a serious electronics n00b =D. I tried to build a system as shown in the image. I have a photodiode which gives me a clock signal in the range of 200 to 500mV. Frequency will be in the range of 100 to 1000 Hz. I would like to amplify this...
  22. K

    Complete Noise Analysis: to find the minimum detectable signal

    Problem Statement: my aim is to digitalize a 10ns narrow pulse coming from a photo diode with current ranging from 10nA-70mA, as its impossible to cover this dynamic range of >60dB using a single TIA i have an option of separating it to two channels as below using two diodes ofcourse Lowest...
  23. L

    Photodiode -- measure power

    Hello, I would like to measure power from a photodiode. How do I go about doing this? What would the circuit look like?
  24. M

    Understanding Photodiode Behavior in Reverse Bias Circuits

    Hi all, I'm having a little bit of trouble understanding photodiodes in reverse bias. Say for instance I have the circuit shown, If I'm asked for a certain voltage required to switch on RA I understand that this corresponds to a certain current being allowed through the diode which corresponds...
  25. B

    Simple photodiode connected to lock-in amplifier

    Hello. I am currently modifying a semiconductor experiment. A laser beam is modulated with an acousto-optical modulator and illuminate the semiconductor sample. The sample is probed by microwaves. The reflected microwave signal go through a demodulator, and then in a lock-in amplifier. Then I...
  26. A

    Working principle of the photodiode and photoresistor

    Hello everyone. I feel myself a little bit confused because I can't understand the difference between the working principle of the photodiode and the photoresistor. The photoresistor changes its resistance under the influence of light while photodiode changes the current across iself. Is this...
  27. B

    Designing Photonic Integrated Circuit: Photodiode to CMOS

    I am now trying to design a photonic integrated circuit which will be used to replace the global interconnect layer of a LSI. I need to somehow take the output of a photodiode w/o TIA (10G signal perhaps) and then transmit that signal to other layer of the LSI by TSV or something. Assume a...
  28. J

    Transistor / Photodiode Circuit Switch Analysis

    Homework Statement Firstly, this is more of a schoolwork issue, not coursework or a set task. It is more to do with understanding the circuit seen in the image provided: I am trying to understand why this circuit does what it is supposed to; activate the lamp when a certain light intensity is...
  29. R

    Difference between ohmic contact and schottky contact

    Hi guys!, i want to know the advantages/disadvantages of using ohmic contact and schottky contact, because i will fabricate a photodiode (p-n junction) and lot of the articles say that ohmic contact is the best for this kind of device. But schottky contact rectify the signal which is more...
  30. Paradox101

    Detecting Lasers with photodiodes---Circuit layout?

    For a certain science fair working model, what should I use to detect the collimated light of a HeNe laser(in the red;653nm if that is necessary)?After some surfing on the net, I found that I should use a 'photodiode'. The desired result should be solely to detect whether the laser's light is...
  31. T

    Photodiode - Reverse Bias Operation

    Hello, I'm attempting to use a photodiode as a light intensity sensor. However, I have a question regarding the operation of a photodiode in a reverse biased position. The current going through the photodiode is dependent on the light received, and is not affected much by the reverse biased...
  32. V

    Photodiode current estimate in an Infrared Proximity sensor

    I am trying to estimate a current which I can get from the photodiode in a simple proximity sensor application having a IR LED emitter and a photo-diode detector. The LED and the photodiode are mounted in the same plane, on a PCB board, and separated about 10mm. If I have a flat Lambertian...
  33. S

    Where Can I Find Diodes for Line-Shaped Beams in Soft X-Ray Experiments?

    I have successfully tested my read-out & data acquisition electronics for the Moxtek XPIN-XT Detector. I cooled the PIN diode below -30°C and found an energy resolution better than 300eV (@8keV) up to 50k cts/sec. Right now I am looking for diodes for line-shaped beams, i.e. about 14mm x 2 to...
  34. R

    Photodiode : ask help too find 10x calculation error

    Hello Can anybody help me find my mistake in the following reasoning for light falling on a photodiode : "When 0.1464 watts/m2 fall on a 7.34 mm2 window, 1.07E-06 watts will penetrate and for a 0.38 A/W photodiode will produce 4.08E-07 amps which, across a 100k resistance will produce 0.0408...
  35. H

    Photodiode Amplification

    I am using (attempting to at least) a photodiode to count fringes from a Michelson interferometer. Here is the amplification circuit I am using: Coming out of the op-amp into the comparator I get about 4.2V in a well lit room, 2.17V in total darkness, and 2.33V when the brightest part of the...
  36. G

    Junction Capacitance in a GaAs Photodiode

    I am trying to get an estimation the junction capacitance of my GaAs Photodiode with respect to varying bias voltages. My Semiconductor Physics online textbook gives the following equations with ε0 = permittivity of free space εGgAs = GaAs dielectric constant μ = Mobility of...
  37. N

    Photodiode and negative resistance

    Our professor has asked us why would a photo diode when shined with light, produce no negative resistance. So far, the only thing I can come up with is because it is in photo conductive orientation (as opposed to photo voltaic) increasing Dark Current thereby eliminating the negative...
  38. Q

    PIN Photodiode, High Voc, Low Isc

    I am working with a silicon PIN-type photodiode in photovoltaic mode, conducting measurements of open-circuit voltage and short-circuit current for varying intensities of incident light. The light is being measured as a proxy for another quantity, and so I must apologise for I can give no...
  39. B

    Photodiode to dim a led in bright light and brighten in dim light

    Hello everyone! I'm currently working on something and am finding myself a little stuck. I am trying to determine how to use a photodiode to brighten leds in low light conditions and dim in bright light conditions. I was able to do this with a simple pnp transistor, however, i need to be able...
  40. A

    Questions using photodiode circuit to measure laser intensity

    Hello all, I'm a new Mechanical engineering graduate student who needs help using a photodiode. I'd like to rig up some kind of circuit that will let me measure the intensity of laser light. This is kind of a new area for me haven't really done anything like this before so forgive me if I come...
  41. L

    Multi LED circuit controlled by photodiode

    Hi, so. I don't know a lot of electronics but this is effectively what I'm trying to create: A photo diode controls the circuit, I assume they give out a current proportional to the intensity of the light it receives. The ciruit, depending on the light intensity will light up different...
  42. P

    Output voltage of a photodiode

    Hello everyone! I'm trying to figure out how to calculate the output voltage of a photodiode in the photovoltaic mode. I want to generate about 5-10V using lasers and a series of photodiodes without using an op-amp (just Vout of the photodiode equvivalent circuit). If I could get any help...
  43. K

    Photodiode in parallel with resistor and capacitor

    hello , I am trying to detect a laser pulse with a photodiode , having a power of 100w max of the laser beam with pulse wave of 1microsecond . when i see the output in ocilloscope the wave do not have 1 microsencond this is without any resistor or capacitor. so my question is that what...
  44. L

    Laser connected to photodiode to measure potential?

    Homework Statement I am doing a lab and need to understand how laser light from a HeNe laser goes into a Si photodiode connected to a lock in amplifier, which I believe is simply a device for measuring potential, works. Homework Equations The Attempt at a Solution This lab was...
  45. G

    Trying to increase the voltage out of a photodiode.

    I have an impulse of ~200mV, ~50nA for about 0.15 seconds. To interface with my circuit, I need it to be 1V+. The problem is, I don't want to use an opamp, or something else that needs to be constantly powered. An ideal solution would be a relay or a FET that has a gate threshold in the...
  46. T

    Photodiode related enquiries

    i have some questions regarding photodiodes, made obvious by my title, so here it is: - is it true that when a photodiode is in forward biased, it acts just like a normal diode? If so, then does it still receive photons from outside sources? if so, then does the photons received affected the...
  47. Artlav

    Using a photodiode in near darkness

    Hello. How can get maximum sensitivity out of a photodiode? So far the best result i got is by using a current-to-voltage amplifier: But with R at 1 MOhm it's still not good enough, and any more causes the thing to start oscillating out of control. Would adding another amplifier...
  48. H

    Why photodiode is operated in reverse bias?

    why photodiode is operated in reverse bias?? can anyone please explain why photodiode is operated only in reverse bias?? can we operate it forward bias state also??
  49. N

    CCD vs Photodiode: Which is Best Detector?

    Which is the preferred detector, the CCD chip or the Photodiode. What are the differences between these two?
  50. I

    Experimental question detecting light scattering with photodiode

    Hi, so I am trying to build a cell counting apparatus using light scattering. The setup is a (green) laser shining through a clear bottle full of (Dicty) cells suspended in a stirred solution. The idea is to put a photodetector at some angle by the bottle; a greater cell density should result in...