precision full wave recitifier on a chip?

How about this one:

Hello Bob,

What do you want to measure and from what kind of input signal? RMS to DC or even dB can be done single chip, for example with the AD536.

Basically, if Analog Devices doesn't have a chip with a desired analog conversion function the chances are pretty high that it doesn't exist. But they do have a lot.

Regards, Joerg

Check out Analog Devices AD630 absolute-value chip.

That circuit is more complex than the one in our book (AoE page 188).

Overly-simple active rectifier designs suffer from poor performance at high frequencies, or at low signal levels and moderate frequencies. In the case of Ron Mancini's design, an additional diode, D2, should be added to prevent U1 from swinging more than a diode drop towards -5V during each half cycle, to reduce the slew-rate-limited recovery time. .. in .. ---+- 10k 1% --+-- 10k 1% ----, .. | % | D2 sd101 | improved version .. | +---|>|-----, | of Ron Mancini's .. | | __ | | 2003 EDN design. .. | '---|- \ U1 | | .. | | >---+ | .. | gnd ---|+_/ | | .. | D1 sd101 | | .. '-- 4.7k ---+---|---+--+--- .. ,---|-_/ | .. | | .. '-----------'

In this design, U1's output has to quickly swing two diode drops during each half cycle, and the time it takes to do this limits its performance.

At low signal levels one can't simply apply the datasheet slew-rate spec, because that value assumes a large input error (AoE page 403-410). In many types of advanced active-rectifier designs, the issue becomes one of reducing the voltage swing necessary to drive any nonlinear elements (e.g. using extra compensation or clamp pins in an opamp), or finding ways to speed it up (e.g., higher slew rate at lower input-error voltages).

--
 Thanks,
    - Win

Amusing. Idea dates to 1982. See my improved version as "FullWaveRectifier.pdf" on the S.E.D/Schematics page of my website.

...Jim Thompson

--
|  James E.Thompson, P.E.                           |    mens     |
|  Analog Innovations, Inc.                         |     et      |
|  Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    |
|  Phoenix, Arizona            Voice:(480)460-2350  |             |
|  E-mail Address at Website     Fax:(480)460-2142  |  Brass Rat  |
|       http://www.analog-innovations.com           |    1962     |
             
I love to cook with wine.      Sometimes I even put it in the food.

See "FullWaveRectifier.pdf" on the S.E.D/Schematics page of my website.

...Jim Thompson

-- | James E.Thompson, P.E. | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona Voice:(480)460-2350 | | | E-mail Address at Website Fax:(480)460-2142 | Brass Rat | |

| 1962 | I love to cook with wine. Sometimes I even put it in the food.

Amusing. Idea dates to 1982. See my improved version as "FullWaveRectifier.pdf" on the S.E.D/Schematics page of my website, which I've been using since that date.

Even with mid '80's OpAmps I was able to rectify 400KHz signals accurately.

...Jim Thompson

--
|  James E.Thompson, P.E.                           |    mens     |
|  Analog Innovations, Inc.                         |     et      |
|  Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    |
|  Phoenix, Arizona            Voice:(480)460-2350  |             |
|  E-mail Address at Website     Fax:(480)460-2142  |  Brass Rat  |
|       http://www.analog-innovations.com           |    1962     |
             
I love to cook with wine.      Sometimes I even put it in the food.

Thanks all. I need 8 of em to sniff 8 audio channels.. using an 8 ch a/d avr.... I showed the standard 2 opamp fwr abs val to the layout guy... he says... dont they have that on a chip yet.... guess he didnt want to draw 8 of em... thought I'd ask.......

You and what ONE other person would buy it ?:-)

...Jim Thompson

-- | James E.Thompson, P.E. | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona Voice:(480)460-2350 | | | E-mail Address at Website Fax:(480)460-2142 | Brass Rat | |

| 1962 | I love to cook with wine. Sometimes I even put it in the food.

Bet they said that to the guy that wanted a 3 opamp instrumentation amplifier.

Yes, it's old... Much older than 1982.

I started using active rectifiers in 1968 or thereabouts, and we described them for AoE in 1978. I advanced to log versions 1972.

400kHz per se isn't so tough; it's the combination of low signal levels (as in wide dynamic-range detectors) and high frequencies that gets difficult. I have a design that works up to 1MHz, yet retains

Hey, so you are one of the two authors of AoE! Wow!

-- Per rispondermi via email sostituisci il risultato dell'operazione (in lettere) dall'indirizzo

I didn't say it was the same, there are probably five or six good configurations. Our full-wave circuit is on page 221 (another is on page 469). I prefer ours because both amplifiers have grounded summing junctions, which is arguably better at high frequencies, because the opamp's CMRR performance isn't put to the test.

Do you like your fixed-up EDN version better? Fewer resistors?

Maybe, that's what happens when you are older. But I'm sure there must have been a few good circuits in the 40s and 50s using tubes.

--
 Thanks,
    - Win

I have added a copy of an article from the 11/25/82 EDN (where I first saw the two-OpAmp FW Rectifier described) to "FullWaveRectifier.pdf" on the S.E.D/Schematocs page of my website. (I save everything :)

Way back then, realizing the floating-summing-node problem, I marked up the article with the extra diode.

I don't see anything resembling this configuration in AoE.

I was using active rectifiers before you were a pup ;-)

...Jim Thompson

--
|  James E.Thompson, P.E.                           |    mens     |
|  Analog Innovations, Inc.                         |     et      |
|  Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    |
|  Phoenix, Arizona            Voice:(480)460-2350  |             |
|  E-mail Address at Website     Fax:(480)460-2142  |  Brass Rat  |
|       http://www.analog-innovations.com           |    1962     |
             
I love to cook with wine.      Sometimes I even put it in the food.

The LM3915 data sheet has several rectifier circuits, including a 'precision full-wave peak detector' using a dual op-amp.

--
Regards, John Woodgate, OOO - Own Opinions Only. 
The good news is that nothing is compulsory.
The bad news is that everything is prohibited.
http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk

See bottom of page 19.

I've used these to clip HDTV video and as 'higher of A or B' (analog OR function) at 30 MHz and they work great. Only quirk: Vh must always be more positive then Vl. GG

hmm, not quite what you want but AD8307 might be worth a look

martin

"An eye for an eye makes the whole world blind" Gandhi

AD8307 not AD8037

martin

"An eye for an eye makes the whole world blind" Gandhi

That is one of my worst consistent errors-- transposing digits 2 and 3 of a 4 digit sequence. BUT, the AD8036/7 does make a good fullwave rectifier. GG

Thanks folks... the 8036 does do a single chip full wave recitifier/absolute value. Never seen one before today! (I looked at that 8307 and was scratching my head.....)