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Favorite precision rectifier

J

Jim Thompson

Jan 1, 1970
0
What's your favorite full wave precision rectifier circuit?

I need something good for sines and triangles of a volt or so, up to 100kHz
or so. I'm looking at this
http://webpages.charter.net/dawill/Images/Precision_FWR.gif
but it has an ugly ~1us propagation delay, resulting in a 200-400mV step at
zero crossing. Eww.

Tim

My favorite:

http://analog-innovations.com/SED/FullWaveRectifier.pdf

I've been using it since the mid '80's, first for a 400KHz
application, back when OpAmp GBW wasn't nearly as good as they are
now.

...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

Isn't the definition of "totalitarian" when the government owns
significant manufacturing; and controls the major media outlets?
 
T

Tim Williams

Jan 1, 1970
0
Phil Hobbs said:
I usually use a Gilbert cell driven by a comparator.

Uselessly overcomplicated.

Has a certain elegance about it though. Breaking it down to its components,
you have a stacked differential amplifier (the mixer) and a high gain
differential amplifier (the comparator), which should have a differential
output to drive the mixer to saturation (or use diode steering). But that's
none other than taking signal x, amplifying the piss out of it to get
100,000x clamped to the supply rails, which is essentially the sign function
(in this case, +1 if x > epsilon, -1 if x < epsilon, x/epsilon if |x| <
espilon). So it generates sign(x) * x, which is another way of writing |x|.
Neato.

Tim
 
J

Jim Thompson

Jan 1, 1970
0
Uselessly overcomplicated.

Has a certain elegance about it though. Breaking it down to its components,
you have a stacked differential amplifier (the mixer) and a high gain
differential amplifier (the comparator), which should have a differential
output to drive the mixer to saturation (or use diode steering). But that's
none other than taking signal x, amplifying the piss out of it to get
100,000x clamped to the supply rails, which is essentially the sign function
(in this case, +1 if x > epsilon, -1 if x < epsilon, x/epsilon if |x| <
espilon). So it generates sign(x) * x, which is another way of writing |x|.
Neato.

Tim

Often the only way when you have 500MHz signals to deal with.

...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

Isn't the definition of "totalitarian" when the government owns
significant manufacturing; and controls the major media outlets?
 
J

Jim Thompson

Jan 1, 1970
0
If you're doing a discrete (not ICs) design, it's arguably a lot simpler than
building the equivalent op-amp-style circuit... we're talking, what, no more
than a dozen transistors here (current sources included), right?

I sense a "fewest number of transistors absolute value circuit" design
challenge coming on. :)

That ought to produce some real crap designs ;-)

...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

Isn't the definition of "totalitarian" when the government owns
significant manufacturing; and controls the major media outlets?
 
J

Jim Thompson

Jan 1, 1970
0
Generally I use an array, e.g. an MC1496.

Cheers

Phil Hobbs

An MC1496 is NOT an array... it's the real deal ;-)

...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

Isn't the definition of "totalitarian" when the government owns
significant manufacturing; and controls the major media outlets?
 
J

Jim Thompson

Jan 1, 1970
0
I usually use a Gilbert cell driven by a comparator.

Cheers

Phil Hobbs

Like-a dis...

http://analog-innovations.com/SED/AM-Demodulator-MC1496.pdf

...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

Isn't the definition of "totalitarian" when the government owns
significant manufacturing; and controls the major media outlets?
 
T

Tim Williams

Jan 1, 1970
0
Phil Hobbs said:
Yep, but it's becoming hard to get.

AAMOF, I have a few LM1496S (TO-5 style!) in my parts box. Removed from
some TV modulator equipment. Some CA3026s and TL442s, too.

Tim
 
T

Tim Williams

Jan 1, 1970
0
Intristing.

Sounds horrendously expensive (well, of course it is, it's AD).

Tim

--
Deep Friar: a very philosophical monk.
Website: http://webpages.charter.net/dawill/tmoranwms

What's your favorite full wave precision rectifier circuit?

I need something good for sines and triangles of a volt or so, up to 100kHz
or so. I'm looking at thishttp://webpages.charter.net/dawill/Images/Precision_FWR.gif
but it has an ugly ~1us propagation delay, resulting in a 200-400mV step at
zero crossing. Eww.

Tim

See page 19, figure 12 of the Analog Devices AD8036 datasheet.

http://www.analog.com/static/imported-files/data_sheets/AD8036_8037.pdf

 
C

Clifford Heath

Jan 1, 1970
0
Phil said:
Yep, but it's becoming hard to get.

I see it listed at 12 of the 21 distributors indexed by
http://findchips.com - but none at 25c - is that where
you're encountering difficulty? Mind you, 35c doesn't
seem too much to pay.
 
J

Jim Thompson

Jan 1, 1970
0
Intristing.

Sounds horrendously expensive (well, of course it is, it's AD).

Tim

Deep Friar: a very philosophical monk.
Website: http://webpages.charter.net/dawill/tmoranwms



See page 19, figure 12 of the Analog Devices AD8036 datasheet.

http://www.analog.com/static/imported-files/data_sheets/AD8036_8037.pdf

G?

And single source, _top_poster_ with misplaced separator :-(

...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

Isn't the definition of "totalitarian" when the government owns
significant manufacturing; and controls the major media outlets?
 
J

Jim Thompson

Jan 1, 1970
0
What's your favorite full wave precision rectifier circuit?

I need something good for sines and triangles of a volt or so, up to 100kHz
or so. I'm looking at this
http://webpages.charter.net/dawill/Images/Precision_FWR.gif
but it has an ugly ~1us propagation delay, resulting in a 200-400mV step at
zero crossing. Eww.

Tim

If you had simulated that circuit you would have seen that
"undershoot".

If you had simulated my submission, you'd still see some "undershoot",
though significantly less.

There's a specific reason for that. Study both versions and try to
discern the difference... Left as an exercise for the student ;-)

...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

Isn't the definition of "totalitarian" when the government owns
significant manufacturing; and controls the major media outlets?
 
T

Tim Williams

Jan 1, 1970
0
Jim Thompson said:
And single source, _top_poster_ with misplaced separator :-(

Mmm?

stratus' post didn't autoindent for some reason. I can't be bothered to
edit it. Short, general comments go at the top. Easy to understand. My
sig was correctly placed, and correctly formatted. That leaves one thing,
top poster prejudice. In that case, go **** off and die, I could care less.

Tim
 
T

Tim Williams

Jan 1, 1970
0
Er well, that's fairly obvious. It goes through two op-amps.

Tim
 
J

Jim Thompson

Jan 1, 1970
0
Er well, that's fairly obvious. It goes through two op-amps.

Tim

Er well, that's not why, and you have no clue about circuits.

Further exhibits: Your stupid top posting AND your ignorant/improper
placement of hyphen-hyphen-space.

Sheeeeesh!

**>--
Deep Friar: a very philosophical monk.
Website: http://webpages.charter.net/dawill/tmoranwms

...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

Isn't the definition of "totalitarian" when the government owns
significant manufacturing; and controls the major media outlets?
 
J

Jon Kirwan

Jan 1, 1970
0
Seems to be a mistake- shows 0.38 above as price in multiples of 2500
(sometimes). Digikey 0.383, Avnet 0.364 in 1-reel lots.

Yeah. However, I tried an order of 2500 just on a lark. (I am
willing to spent $70.) I got this confirmation:

Subject: Order Request Accepted
From: "Arrow Electronics Inc." <[email protected]>

Thank you for placing an online order with Arrow Electronics,
Inc. Your Order #: xxxxxx

Your order request, placed on xxxxxxxx, has been received.

Please save this email or print it out; it will serve as the
detailed STATEMENT of charges posted to your credit card. An
invoice will not be mailed with your order so please retain a
copy of this email for your records.

Item Qty Part/Description/Supplier Price
1 2500 MC1496DR2/ON Semiconductor $0.03

Subtotal: $70.50
Applicable Sales Tax: $0.00
Shipping/Energy Surcharge: $8.99

Total: US$79.49

We shall see if the reel arrives.

Jon
 
J

Jon Kirwan

Jan 1, 1970
0
<snip>
We shall see if the reel arrives.

Yup. 2500 of the beasties _DID_ arrive. All nicely done up in a full
reel. Cost me 3.1796 cents each after shipping costs are included.

So, anyone looking for a supplier of cheap 14-pin SOIC MC1496's? ;)

Jon
 
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