Want to build an electrical circuit, a sensor (INFRED) connected to an amplifier that ,
requirements:
1. Wavelength falling on sensor 900nm.
2.light intensity 5mW\cm2 * (2mm*2mm).
3. Want the accuracy level of the circuit to be very large .
What components must I use to get good results?
Hi Ward,
What components must I use to get good results?
As Michael suggested, there are wide ranges of photodiode sensors and manufactures will meet your requirements. Most Si bassed photodiode sensor should peak at the photo sensitivity near 800-900nm in the NIR region. So other operating parameters become important, such as source capacitance (sensor speed), operating temperature, circuit gains etc.. I am trying to find you a reliable, rugged, low noise, low NEP and high quality photodiode sensor.
You are looking for light intensity 5mW\cm2 * (2mm*2mm) or 5mW/cm^2 * 0.04 cm^2 = 0.2 mW @900nm. If I assumed the photo sensitivity of 0.3A/W @900nm, the maximum current can be 0.3A/W * 0.2mW = 0.06mA or 60uA, which are not difficult to find from mouser, digikey or newark and other distributors.
One of our high sensitive TIA op amp is LMP7721, but based on the uA input current range, the application may not require it.
What are available power supply rails in your application?
What is desired TIA output voltage?
What is the NIR sensing application? Is it for communication?
What types of light source is from 900nm? Is it a NIR laser diode?
Below is an example of TIA circuit with LMP7721. Please let us know the above requirements.
Best,
Raymond
Hi Ward,
If you want to follow the TIA application note, it will be good, if your application is identical or similar.
Enclosed is the simulation of the detector, since the photo sensor specification has changed. You may follow the application note and make further modification.
Please keep in mind the light incident angle of the detector is very specific or approx. 10 degrees. The sensor is suited for the application below, which is not a precision light detection. If the application's light source is narrow band approx. 900nm, then you may need to make some adjustment in the TIA's gain resistor. Currently 135uA of typical current is specified from 1000 lux, standard light A source (broad band light spectrum). If you use narrow band 900nm light source, the typical current figures are required to be re-characterized or measured.
Based on your requirements, this is a likely laser diode NIR source with uniform emitted light intensity. You will be better off to have flat glass substrate rather than epoxy mounting lens in front of sensing element, especially this is a precision mounting application. With epoxy LED type of mounting, you may encounter optical alignment issues if the collimated light beam has specific diameter and not project on the detector consistently. Again, the selection of the photo diode packages/mounting may depend on the application, which I do not have information of.
If you have additional questions, please let us know.
Best,
Raymond
