I’ve gotten a lot of questions on the blog about the new version of the MHS5200A function generators available on eBay. Viewer Tolga was kind enough to send one in to me to review and tear down. Although some improvements have been made over the older models, there are some concerning issues with these new models too!
I recently designed an infrared sensor board (dubbed “IRis”) for my friend’s Defcon talk. This video walks through the circuit design of the photodiode amplifier, and discusses some of the pitfalls associated with photodiode amplifier design.
Schematics, BOM, and KiCAD design files for the described IRis board are available on github.
References and additional reading:
|The bible of photodiode amplifier design||Photodiode Amplifiers: Op Amp Solutions, Jerald Graeme|
|Good overview of photodiode design concerns||Common Photodiode Op-Amp Circuit Problems and Solutions, Digi-Key|
|Excellent photodiode amplifier reference design||Photodiode Amplifier Reference Design, Texas Instruments, John Caldwell|
|Bob Pease’s musings on transimpedance amplifiers||What’s All This Transimpedance Amplifier Stuff Anyhow?, Bob Pease|
|JFETs as ultra-low leakage diodes||Current Sources and Voltage References, Linden T. Harrison, Chapter 6.6|