Lock-In-Amp on a chip?

James P. Meyer

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Mar 26, 1997, 3:00:00 AM3/26/97

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Has some manufacturer integrated a complete LIA or at least the
major components on a chip in the last 5 years?

The last time I needed one, I built it up from op-amps, DG212
cmos switches, and active filters. I'm looking at about 10 KHz for the
basic chopping frequency. I've got control over the chopping, so I don't
need a PLL to recover the reference.

Jim

Bill Sloman

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Mar 27, 1997, 3:00:00 AM3/27/97

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This is a trifle off the wall, but you might look at the Analog Devices
AD598 LVDT signal conditioner. It probably won't be suitable for your
application, but it has more or less the right facilities built in.

Bill Sloman (slo...@sci.kun.nl) | Precision analog design
TZ/Electronics, Science Faculty, | Fast analog design and layout
Nijmegen University, The Netherlands | Very fast digital design/layout
| e-mail for rates and conditions.

Winfield Hill

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Mar 27, 1997, 3:00:00 AM3/27/97

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John Wettroth, <jw...@mindspring.com> said...

>
>James P. Meyer <jim...@acpub.duke.edu> wrote:
>>
>> Has some manufacturer integrated a complete LIA or at least the

>> major components on a chip in the last 5 years? [snip]
>
> I'm nearly positive that there are no monolithic Lock-In-Amps. ...

The synchronous rectification portion of a lockin amplifier is available
from several manufacturers. On page 1031 of AoE, we show an inverting
opamp with a spdt CMOS switch like a 4053, and also mention the Analog
Devices AD630 phase-reversing amplifier, which contains both of these
functions. We discuss the NE5520 chip on page 1001, which includes the
sine-wave excitation. This chip, which is aimed at the LVDT market, is
nonetheless a nice general-purpose lockin chip. I have used it for
example, in a low-level ac-excitation strain gage signal conditionor,
adding only an ac input amplifier and dc output filtering.

Finally, any good 4-quadrant multiplier, such as an AD734, is also a
synchronous rectification "chip." If you have low-distortion sine-wave
excitation, the linear multiplier features a non-responsiveness to
harmonics, without requiring a pre-filter.

--
Winfield Hill hi...@rowland.org _/_/_/ _/_/_/_/
The Rowland Institute for Science _/ _/ _/_/ _/
Cambridge, MA USA 02142-1297 _/_/_/_/ _/ _/ _/_/_/
_/ _/ _/ _/ _/
http://www.artofelectronics.com/ _/ _/ _/_/ _/_/_/_/

user

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Mar 29, 1997, 3:00:00 AM3/29/97

to James P. Meyer

James P. Meyer wrote:
>
> Has some manufacturer integrated a complete LIA or at least the
> major components on a chip in the last 5 years?
>

> The last time I needed one, I built it up from op-amps, DG212
> cmos switches, and active filters. I'm looking at about 10 KHz for the
> basic chopping frequency. I've got control over the chopping, so I don't
> need a PLL to recover the reference.
>

> Jim

The AD630 is an integrated solution offering the input amplifiers and
switching functions required to implement a LIA. You add your own filter
at the output and thats it really.

cheers

David
--
Dr. David Moodie
Optoelectronics Division
Strathclyde University
204 George Street
Glasgow G1 1XW

tel +44 (0)141 552 4400 ext 2950
fax +44 (0)141 553 1955
e-mail d.mo...@strath.ac.uk