Photodiode Definition and 72 Threads

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. R

    How to convert photodiode voltage to any photonic unit

    How can I convert the voltge measured across a photodiode to light output or intensity or any other photonic unit? I am trying to measure the light intensity/output of some LEDs using a photodiode but the photodiode measures voltage as a function of light intensity.
  2. P

    Calculating Irradiance from BPW21R Photodiode Current

    I am using a BPW21R photodiode to measure irradiance instead of a BPW21 photodiode in a pyranometer circuit that could be found in the pdf link below. How should I calculate irradiance(W/m^2) from the current produced in a transimpedance amp circuit if there is no Spectral...
  3. K

    Understanding the Significance of Photodiode Bandwidth | Lab Tips

    What does the bandwiidth of a photodiode signify? I just know that it is related to speed of photodiode, but while dealing with PD practically in lab. , what does its bandwidth tell me ?
  4. B

    Photodiode Sampling: How Does Wavelength Affect Plate Saturation

    I am curious how does the wavelength of light let's say 800nm/s collected by a photodiode results from the saturation of the plate 1mm. sq. I have this photodiode from a cdrom and it has 6 legs, two do not have a bias-junction, the other four do, and the collector is slightly greenish. I...
  5. J

    Calculating photodiode current and voltage

    Hi I'm pretty new to the forums. I've been searching and can't find anything on this. Can anyone show me how to calculate the current/voltage produced by a photodiode?
  6. M

    Help required for surface reflection circuit (IR-LED/ PHOTODIODE)

    Hi I am new to this forum but have been interested in reading many threads and would like to know if any of the experts could help. I am looking to make a circuit that I can measure different output levels of a photodiode from the amount of "signal" reflected onto it from a particular...
  7. A

    How to Design a 4-20mA Circuit for a Photodiode with Variable Light Intensity?

    Homework Statement Okay so I've got a photodiode with reverse current linear dependence of 0.3uA/Lux and dark current of 20nA. I need to design a circuit (4-20mA current transmission system) with 4mA at zero light intensity and 20mA at 4x10^4 Lux. The Attempt at a Solution Struggling! I...
  8. M

    IR Photodiode or Phototransistor?

    Hi guys! I'm a beginning EE students, and haven't taken many courses yet (haven't even covered transistors in my circuits class yet-- we're up to diodes, woo!). For a "for fun" project, I've been messing around with the Arduino microcontroller...
  9. Topher925

    Is the quantum efficiency of a photodiode dependent upon its temperature?

    Like the title states, is the voltage produced by a photodiode, or any PV device for that matter, dependent upon that devices temperature? To rephrase, if you have a fixed amount of photons coming in contact with the business end of a photodiode, is the voltage or current generated by the...
  10. J

    Need Help wiring a photodiode to measure light

    Hi everyone, I'm new to the forum and basically need help to build a little gadget to measure the intensity of light that passes through a tube filled with solutions of different dye concentrations. I have a 10530DAL photodiode, and a light source. What I'm doing now is measuring the...
  11. B

    Pixel, photodiode and capacitor

    Hi! I'm having trouble figuring out the difference between a pixel and a photodiode as well as a capacitor- they all seem like the same property to me! :confused: Can someone please help me?:confused: Thanx
  12. B

    Understanding the Difference Between Pixel and Photodiode: Expert Help

    Pixel + Photodiode!help Hi! I don't know if this is the right place for this topic but I could not find "Digital Technology" elsewhere so here I go: I'm having trouble figuring out the difference between a pixel and a photodiode as well as a capacitor- they all seem like the same property...
  13. C

    Time constant of photodiode? parallel stray capacitance?

    Hihi, http://sales.hamamatsu.com/assets/applications/SSD/si_pd_circuit_kspd1043e06.pdf 5. high-sensor From the message there, I don't understand what is the meaning of time constant of resistor? Why does it say that the time response of the circuit depends on the time constant...
  14. S

    Improving Photodiode Circuit Performance: Understanding Slow Rise Time Issues

    Hi, I have a photodiode circuit (attached), where a photodiode is hooked up to a current to voltage opamp connected to a voltage divider. This circuit works as intended: when there is light, Vo ~ 3.3V, and when there is no light, Vo ~ 0.3V. However, when I measured the rise time of this...
  15. S

    Problem in taking voltage signal from photodiode to labview

    Hi frnds, I have the photodiode DET10A and I am trying to take its output to computer using USB-6008. Labview feels that the DAQ’s ports are open and shows values 1.4 – 1.42. However, when I connect the photodiode to a multimeter or oscilloscope I see correct signal. the maximum photodiode...
  16. S

    Photodiode & EMF: Is This Correct?

    Just thought i would ask, when a photodiode is acting in reverse bias, it allows current to pass but does not generate voltage. In fact, it has a voltage drop. When in forward bias, it allows current to pass but also generates an EMF. Is this correct, any response would be appreciated.
  17. C

    The + sign above the photodiode, what does it mean?

    I don't really have much knowledge of electronics and kindly seek your helps. The + sign above the photodiode, what does it mean? Does it mean I have to connect the cathode to the ground?? Then, about the direction of the current, why does the current flow from cathode to anode? I...
  18. S

    Understanding Photodiode Behavior: Negative Voltage and Current Explained

    Hey guys, just another question regarding photonics. From looking at an I - V characteristic of a typical photodiode: http://www.rp-photonics.com/img/photodiode.png I don't understand what it means by there being a negative voltage and a negative current. I suspect the negative in the current...
  19. T

    Phototransistor vs photodiode ?

    HI all, i'm currently working with IR sensor diodes, and trying to find a proper device for my project, however i haven't found a good unit which fills my needs. Now that i have extended my search to phototransistors, i wonder are they compatible with photodiodes? Im using Atmel's...
  20. R

    Finding the Saturation Current of a photodiode in Reverse Bias

    Homework Statement I am trying to finish the equation, to compare it against a set of data so I can then find the accuracy of my results in relation to the equation: I(dark) = I(sat) * e(qV/kT) -1 I have the following data: Va - the applied (bias) voltage q kB - Boltzmann Constant...
  21. M

    Whats the characteristics of a photodiode?

    whats the characteristics of a photodiode? what will its resistance be, if there is a high intensity of IR radiation falling on it, and what will its resistance be, if there is a low intensity of IR radiation falling on it?
  22. I

    Photodiode carrier transit time

    Hello, I am having a bit of trouble with the following problem: Assuming a built in voltage equal to the bandgap voltage, calculate the slowest possible transmit time for a carrier with 5V reverse bias applied to the GaAs photodiode. I would be able to do this problem without difficulty if...
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