Encyclopedia … combined with a great Buyer's Guide!

Sponsoring this encyclopedia:     and others

Using a Current Amplifier for Optical Power Measurements and Recording with a Photodiode

Posted on 2006-10-16 as a part of the Photonics Spotlight (available as e-mail newsletter!)

Permanent link: https://www.rp-photonics.com/spotlight_2006_10_16.html

Author: , RP Photonics Consulting GmbH

Abstract: This article discusses the manifold advantages of using a current amplifier (possibly a commercial device) instead of a simple electric circuit for optical power measurements with photodiodes. The gained flexibility and efficiency are very much worth the cost of a good current amplifier.

Dr. Rüdiger Paschotta

Ref.: encyclopedia article on photodiodes

Honestly, it looked to me like a complete overkill when many years ago a colleague of mine suggested to buy a commercial current amplifier (also called transimpedance amplifier) for various kinds of measurements with a photodiode in our laboratory. After all, couldn't I just use a very simple home-made circuit, consisting of nothing more than a small battery and a resistor? In this way I could apply some reverse voltage to the photodiode and convert the photocurrent into a voltage, which I could then easily measure with a multimeter or monitor with an oscilloscope. The cost for that would be a tiny fraction of that of a commercial current amplifier.

Well, in principle this works, but I soon learned to appreciate the advantages of the current amplifier:

Having used this kind of equipment, never again would you bother to save some money by using a simple resistor/battery circuit instead of a current amplifier, when you need flexibility in the laboratory! You may, however, consider to build such a device yourself, or let your electronics support build one. If you don't require top performance, but need several of those devices in your lab, this can be a reasonable solution.

For high-speed applications or in cases where you need ultimate sensitivity, a universal current amplifier may no longer be suitable. Here, you have to get the amplifier as close as possible to your photodiode – ideally, built into the photodiode housing. For such purposes, there are reasonably prized current amplifier modules, if you don't want to get into the electronics details.

This article is a posting of the Photonics Spotlight, authored by Dr. Rüdiger Paschotta. You may link to this page and cite it, because its location is permanent. See also the RP Photonics Encyclopedia.

Note that you can also receive the articles in the form of a newsletter or with an RSS feed.

Questions and Comments from Users

Here you can submit questions and comments. As far as they get accepted by the author, they will appear above this paragraph together with the author’s answer. The author will decide on acceptance based on certain criteria. Essentially, the issue must be of sufficiently broad interest.

Please do not enter personal data here; we would otherwise delete it soon. (See also our privacy declaration.) If you wish to receive personal feedback or consultancy from the author, please contact him e.g. via e-mail.

Your question or comment:

Spam check:

  (Please enter the sum of thirteen and three in the form of digits!)

By submitting the information, you give your consent to the potential publication of your inputs on our website according to our rules. (If you later retract your consent, we will delete those inputs.) As your inputs are first reviewed by the author, they may be published with some delay.


If you like this page, please share the link with your friends and colleagues, e.g. via social media:

These sharing buttons are implemented in a privacy-friendly way!