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lock-in amplifier using AD630 or ADA2200.


I want to built a lock-in amplifier with a LO frequency below 5kHz. I am little confused about the choice between AD630 and ADA2200. The performance is the main concern in my application (not the power consumption nor the price). How can I choose the best part: what are the main specifications to look at? And what would be better as a preamplifier: a low noise transimpedance amplifier (such as AD8067, ...) or an input amplifier (such as ADA8429, ...)?

Thank you very much for your answer.


  • Hello,

    Thanks for the email. The AD630 performs as a synchronous detector and was designed as a LF averaging detector. When I see the term LO I associate it with a PLL. The AD630 isn't a PLL, if that is what you need. The original targeted application was to extract very-low amplitude directional information from LVDTs and performs very well at that. However there is no phase detector or I and Q detection and so does not emulate a true PLL.

    I'm not an expert on the ADA2200, and I know of no comparison studies between the 2 parts. Contact Brian Harrington

    for further info on ADA2200.



  • Hello Thomas,

    There is a third option that may provide the best performance.  That is the LTC6943. If you look on page 10, there is a schematic for a lock-in amplifier.  This circuit may perform the other 2.  It is hard to say.  One key metric of performance for a lock-in amplifier is the integrated noise over its output bandwidth.  But there are other metrics.  They need to be considered in the context of the application.