# Measuring Pulsing Current Output Average From Photodiode

• SHalas1
In summary, the conversation discusses using a photodiode to measure optical power, with the photodiode converting the power into a current. The optical power pulses rapidly in 15 ns periods with a 5 ns on-time and a 1 ns rise and fall time. The speaker is looking for an analog averaging solution using an op-amp circuit to obtain voltage outputs every 1 us that are equivalent to the average voltage over the past 1 us. They ultimately need to read the average voltage every 5 us, but are interested in oversampling at a rate of 5X to ensure accurate readings. The speaker has considered using "fast integrator op-amp" circuits, but is unsure if it will work for their needs.
SHalas1
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, i.e. an op-amp circuit that would give voltage outputs, say, every 1 us that are equivalent to the average voltage over the past 1 us. Ultimately, I need to be able to read the average voltage (proportional to an optical power, of course) every 5 us, but I am interested in oversampling at a rate of 5X in order to ensure I am not missing pulses in my pulse train and getting inaccurate readings. I have looked into "fast integrator op-amp" circuits, but I am still unsure if that will do the trick. Any suggestions would be greatly appreciated.

Thank you!

SHalas1 said:
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, i.e. an op-amp circuit that would give voltage outputs, say, every 1 us that are equivalent to the average voltage over the past 1 us. Ultimately, I need to be able to read the average voltage (proportional to an optical power, of course) every 5 us, but I am interested in oversampling at a rate of 5X in order to ensure I am not missing pulses in my pulse train and getting inaccurate readings. I have looked into "fast integrator op-amp" circuits, but I am still unsure if that will do the trick. Any suggestions would be greatly appreciated.

Thank you!
Welcome to the PF.

Sounds like a fun project. Is your photodiode at the end of a fiber? How is it picking up these light pulses?

The pulse width that you describe is fairly short, so you will need a specialized photodiode detector, IMO. What do you have in mind so far? And the first stage or two of the detector will not be jellybean opamps -- they should be fairly high speed detector amps, it would seem.

## What is a photodiode?

A photodiode is a type of semiconductor device that converts light into electrical current. It is commonly used in various electronic devices such as cameras, solar panels, and optical communication systems.

## How does a photodiode measure pulsing current output average?

A photodiode measures pulsing current output average by converting the light it receives into electrical current, which is then amplified and measured by a current measuring device. The pulsing current output average is calculated by taking multiple readings and averaging them over a specific time period.

## What factors can affect the accuracy of measuring pulsing current output average from a photodiode?

Some factors that can affect the accuracy of measuring pulsing current output average from a photodiode include ambient light, temperature, and the quality of the photodiode itself. Additionally, the circuit used to amplify and measure the current should be carefully designed and calibrated for accurate readings.

## How can the pulsing current output average be improved?

The pulsing current output average can be improved by using a high-quality photodiode, minimizing ambient light interference, and carefully calibrating the measuring circuit. Additionally, the pulsing frequency and duty cycle can be optimized for more accurate readings.

## What are some potential applications of measuring pulsing current output average from a photodiode?

Measuring pulsing current output average from a photodiode has various applications, such as in optical communication systems, laser power monitoring, and light intensity measurements in scientific experiments. It can also be used in biomedical devices for monitoring heart rate and blood oxygen levels.

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