Circuit challenge

Really? I see no graphs, not test data etc..

Tells me nothing. Jamie

Drat! I made a sign error. There's really no need to involve the phase-shifted second signal at all, just an op amp and diode and some resistors.

You measure the difference signal from the source to a doubled-when-positive and ground-when-negative clamp output.

is corrected now.

Not really precise, but it uses only three components.. an LM324 and two RNW4's (no diodes).

Simulation:

The remaining op-amp could be used to generate the inverted signal, if wasn't present.

Best regards, Spehro Pefhany

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How could you possibly not see it? Take that signal amplitude down to 250mV and then get back to us.

It prevents the amp from railing itself, which helps the crossover distortion a lot.

Cheers

Phil Hobbs

This idea?

It needs an output buffer because the output impedance goes from very low for negative inputs to ~23K for positive outputs.

Best regards,

The challenge was for fullwave output with one section.

We know. The challenge has been met. We're talking about other stuff now. Sometimes the other stuff is even vaguely related to the OP's topic and/or electronic design.

Best regards, Spehro Pefhany

--
"it's the network..."                          "The Journey is the reward" 
speff@interlog.com             Info for manufacturers: http://www.trexon.com 
Embedded software/hardware/analog  Info for designers:  http://www.speff.com

I posted this on the 2nd, but have seen no comment...

The switch opens/closes at zero crossing of V2.

I've used this very scheme to do synchronous detection of signals. ...Jim Thompson

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| James E.Thompson                                 |    mens     | 
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I love to cook with wine.     Sometimes I even put it in the food.

one opamp (and diode) as an active half wave rectifier and then added that to the inverse (in a 2nd opamp). I went looking, but couldn't find it (in

2nd edition) If it's a 'requirement' that both phases be used.. then that might work... he'd have to add the two signals by some "clunky" method w/o a 2nd opamp.

Isn't that just hiding a whole bunch of extra stuff it will need.

An analog switch. Didn't the OP allow "extras", except for an extra OpAmp? ...Jim Thompson

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| James E.Thompson                                 |    mens     | 
| Analog Innovations                               |     et      | 
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    | 
| San Tan Valley, AZ 85142   Skype: Contacts Only  |             | 
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  | 
| E-mail Icon at http://www.analog-innovations.com |    1962     | 
              
I love to cook with wine.     Sometimes I even put it in the food.

Don't the select inputs of the switch needed to be driven by some kind of comparator?

Just AC-couple and bias the control at threshold ;-) ...Jim Thompson

-- | James E.Thompson | mens | | Analog Innovations | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | San Tan Valley, AZ 85142 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at

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

That has a limited input of up to ~.6 volts however, it shows that it can drop to near 0 volts and maintain good results.

Jamie

Just use the op amp for the comparator function, and an SPDT switch, was also suggested (I'm not happy using an op amp without hysteresis, but if the switch is a good enough 'low impedance', it DOES work).

CMOS analog switches aren't usually happy with slow-slewing control inputs, there's some power-supply glitching to be expected. And individual MOSFET switches usually have inconvenient clamp diodes for gate protection; the 'bias at threshold' idea is quite idealistic!

Depends on your definition of "low impedance", but this occurred to me while doodling yesterday, waiting for my wife at the beauty shop...

(The circuit actually outputs the greater of two inputs, sinusoidal or whatever.) ...Jim Thompson

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| James E.Thompson                                 |    mens     | 
| Analog Innovations                               |     et      | 
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    | 
| San Tan Valley, AZ 85142   Skype: Contacts Only  |             | 
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  | 
| E-mail Icon at http://www.analog-innovations.com |    1962     | 
              
I love to cook with wine.     Sometimes I even put it in the food.

You can do the same sort of thing with one phase, using a RRO amp with a single supply. Starting with your schematic, put another 1k resistor from the summing junction to the K of D1, and take the output from K just as you're doing now. That makes a unity-gain inverter for negative signals and a series 2k resistor for positive ones.

The advantage is that it doesn't have to slew from the negative rail when the input goes negative--it just has to slew through one diode drop.

Yours needs a negative supply because of the bipolar input on the noninverting input, so you can't avoid the bigger slew artifact at phase

1's negative-going zero crossing.

Cheers

Phil Hobbs

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Dr Philip C D Hobbs 
Principal Consultant 
ElectroOptical Innovations LLC 
Optics, Electro-optics, Photonics, Analog Electronics 

160 North State Road #203 
Briarcliff Manor NY 10510 

hobbs at electrooptical dot net 
http://electrooptical.net

Oh, and ground the noninverting input, of course.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs 
Principal Consultant 
ElectroOptical Innovations LLC 
Optics, Electro-optics, Photonics, Analog Electronics 

160 North State Road #203 
Briarcliff Manor NY 10510 

hobbs at electrooptical dot net 
http://electrooptical.net