Lock-In-Amplifier Prototype Demo

This is a lock-in amplifier circuit I designed and prototyped for a school project for essentially a photodetector semiconductor chip. Of course you can just buy an off-the-shelf lock-in amplifier for thousands of dollars; or if you don't need to run your circuit at a very high frequency, you can make a lock-in-amplifier yourself for less than 50 bucks, like the one in this video.
So here it is, my version of the lock-in amplifier for a photodetector.
Enjoy!

[@iristhevirus]

You need a modulated current source to drive your laser. There are 2 ways: 1) If you are at development stage of your project that nothing is set in stone yet, I suggest to buy bench top laser drivers/current supply from the store. Then what you are looking for on one of those is to have either modulation settings for adjustable frequencies to modulate your laser current, or to have an input for an outside trigger waveform. And for the triggering waveform, just hook up a fcn generator.

[@iristhevirus]

And 2) is just to build a voltage driven current source (time to use your EE skills on transistors). I only need to drive a (inexpensive) laser diode for my project, so no need for complicated current driver for my laser. So I built a voltage driven current source on my board to drive the laser. And I used the same modulated voltage as one of the input for the demodulator at the output. Hope it helps, and good luck!

[@manojitr5292]

One doubt...What demodulator did you use?? AD630
Is it posible to use MC1496 as demod for the lockin??

[@iristhevirus]

I used AD630, and the only reason for that is because the prototyping price and time budget, and I happened to have a number of AD630 laying around so I was able to start the prototyping right away. From glancing at MC1496 datasheet briefly, I believe it will work as well.. I did notice some differences on MC1496, such as higher input bias current, higher common mode rejection, etc. So it really depends on the requirement for your applications.. Good luck!