Bootstrapped Op Amp Articles

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mediatechnology
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Bootstrapped Op Amp Articles

Post by mediatechnology » Wed Oct 22, 2014 3:07 pm

I have quite a collection of articles on bootstrapped op amps.

By bootstrapping I refer to modulating the supply voltage to increase output voltage swing or, in some later examples, to reduce distortion.

Information on current-boosted outputs can be found in the Jim Williams series: viewtopic.php?f=12&t=13
Or here: viewtopic.php?f=6&t=23 here: viewtopic.php?f=6&t=799 and here: viewtopic.php?f=7&t=509


The first installment, an Idea for Design published in 1974 by Surjan Dogra may be the grandaddy of all high voltage-bootstrapped designs.
It was republished and cited by Graeme in "Designing With Operational Amplifiers, Application Alternatives" in 1977.
Dogra's circuit was used a few years later in the MCI JH-500 series to replace the discontinued HA-2645 with a bootstrapped NE5534.


"A Few Extra Components 741 Op Amps For High-Voltage-Swing Applications," Surjan Dogra, Electronic Design, April 26, 1974.

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"A Few Extra Components 741 Op Amps For High-Voltage-Swing Applications," Surjan Dogra, Electronic Design, April 26, 1974

"A Few Extra Components 741 Op Amps For High-Voltage-Swing Applications," Surjan Dogra, Electronic Design, April 26, 1974.
Full pdf:
http://www.waynekirkwood.com/images/pdf ... 6_1974.pdf

Graeme, Burr-Brown, 1977

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Op Amp Supply Bootstrap "Designing With Operational Amplifiers, Application Alternatives," Jerald G. Graeme, Burr-Brown, 1977.
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Re: Bootstrapped Op Amp Articles

Post by mediatechnology » Sat Jan 14, 2017 2:36 pm

The first installment, an Idea for Design published in 1974 by Surjan Dogra may be the grandaddy of all high voltage-bootstrapped designs.
It was republished and cited by Graeme in "Designing With Operational Amplifiers, Application Alternatives" in 1977.
Dogra's circuit was used a few years later in the MCI JH-500 series to replace the discontinued HA-2645 with a bootstrapped NE5534.
The MCI Bootstrapped "Swinging Op Amp" Using an NE5534 "2003" Op Amp

Image
The MCI "Swinging Op Amp" used in the JH-500C console.

MCI originally used the TO-39 2N5679 and 2N5681 PNP/NPN pair.

MCI's 1979 "Swinging" Op Amp Ad in dB Magazine

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MCI Swinging Op Amp Ad dB Magazine January 1979.
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Re: Bootstrapped Op Amp Articles

Post by JR. » Sun Jan 15, 2017 9:23 am

viewtopic.php?f=6&t=289&start=40

Some more general discussion at that other thread... (looks I was pissing people off in 2013 too). :oops:

JR

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Re: Bootstrapped Op Amp Articles

Post by mediatechnology » Sun Jan 15, 2017 12:24 pm

I posted the MCI one since the earlier schematic I had showed elsewhere had 100 nF caps from base to collector.
The correct value was 680 pF.
Someone proposed using a bootstrapped circuit over at DIY Audio...
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Re: Bootstrapped Op Amp Articles

Post by Gold » Sun Jan 15, 2017 5:16 pm

When Neumann started using an LM709 in the VG66 they were always bootstrapped. I'll scan and post the SE66 Input and RIAA encode. The RIAA decode is in the monitor/phono module(s). Some had functions combined in one module and some had functions split between them. There are also different versions of each flavor. A surprise in every rack!

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Re: Bootstrapped Op Amp Articles

Post by mediatechnology » Mon Jan 16, 2017 9:31 am

When Neumann started using an LM709 in the VG66 they were always bootstrapped. I'll scan and post the SE66 Input and RIAA encode.
Wow. Very interesting! I would love to see those scans. I've been looking for a VG66 schematic.
I think they might have done that to extend its slew rate.

I recall a JAES paper where they extended the SR of a 4558:

EIICHI FUNASAKA AND HIKARU KONDOU, "Feedforward Floating Power Supply (High-Response-Speed Equalizer Circuit)," J. Audio Eng. Soc., Vol. 30, No. 5, 1982 May.

http://www.proaudiodesignforum.com/imag ... Supply.pdf

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Wide Bandwidth RIAA Phono Preamp With Feedforward Power Supply

One of the examples is a voltage-boosted phono preamp.

FWIW The Jim Williams series on op amp booster stages is one of the most popular pdf downloads from this site. viewtopic.php?f=12&t=13
It's consistently in the top ten.

Edit March 4, 2017. This thread continued to a discussion of the Neumann SE66 which is now found here: viewtopic.php?f=12&t=865
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Re: Bootstrapped Op Amp Articles

Post by mediatechnology » Sat Mar 04, 2017 2:46 pm

"Bootstrapping Your Op Amp Yields Wide Voltage Swings," Grayson King, Tim Watkins, Analog Devices, EDN, May 13, 1999.
Getting 100v p-p from a monolithic op amp is just one example of what you can achieve by bootstrapping power supplies. “Bootstrapping” in this context is simply a method of controlling a device’s supply voltages based on its output.
http://www.proaudiodesignforum.com/imag ... 3_1999.pdf

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Bootstrapping Your Op Amp Yields Wide Voltage Swings," King, Watkins, EDN, May 13, 1999, Figure 1.
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Re: Bootstrapped Op Amp Articles

Post by mediatechnology » Mon May 08, 2017 7:18 am

"Extending Op Amp Supplies To Get More Output Voltage," Dale Eager, Linear Technology AN-67 pg. 58.

Linear Technology Application Note AN-67 is a treasure trove of circuits. This "suspended supply" voltage-boosted op amp stage, using MOSFETs, was used in a telephone ring generator circuit.

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"Extending Op Amp Supplies To Get More Output Voltage," Dale Eager, Linear Technology AN-67 pg. 58.

Linear Technology Application Note AN-67, September 1996. http://cds.linear.com/docs/en/applicati ... /an67f.pdf

BTW JR it was Brad Wood that pointed out the Funasaka paper (posted earlier) back in 2006 or 2007 when I first wrote about the input-capacitorless "DC-coupled" preamp.
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Re: Bootstrapped Op Amp Articles

Post by plupo » Thu Jul 27, 2017 8:27 am

Dears
I'm quite new on this forum, full with interesting stuff, however this "boosted opamp" series of articles are showing since the start an input positive node that can swing more than the absolute maximum rating vs the power supplies of the OPAMP itself , and you know this' no good.
Those schematics must not be taken "literally" but just as a hint to look for improving the performances ( the only drawing here that gentle manage the issue is the one from Burr Brown old book , that have placed the protection diodes and resistor at the right place) all the rest will make you quite disappointed , burning a series of poor opamps.
Due the fact i'm working on boosted opamps for a new instrument, I'll let people know as soon as a good result will be obtained.
BR
Paolo

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JR.
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Re: Bootstrapped Op Amp Articles

Post by JR. » Thu Jul 27, 2017 8:41 am

plupo wrote:
Thu Jul 27, 2017 8:27 am
Dears
I'm quite new on this forum, full with interesting stuff, however this "boosted opamp" series of articles are showing since the start an input positive node that can swing more than the absolute maximum rating vs the power supplies of the OPAMP itself , and you know this' no good.
Those schematics must not be taken "literally" but just as a hint to look for improving the performances ( the only drawing here that gentle manage the issue is the one from Burr Brown old book , that have placed the protection diodes and resistor at the right place) all the rest will make you quite disappointed , burning a series of poor opamps.
Due the fact i'm working on boosted opamps for a new instrument, I'll let people know as soon as a good result will be obtained.
BR
Paolo
Hi and welcome... Most of these designs with bootstrapped rails will swing the PS in the same direction as the signal output so non-inverting topologies can accept larger input swing than with static (no signal) PS rail voltage.

I won't vouch for any specific design but over the decades I have used variants on this approach several times. Back in the 70's I made a hifi amplifier for my sister using a bootstrapped op amp built into the old chassis and using the power supply from the former failed amp.

JR

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