Quad rail to rail op amps

  • Thread starter Ravaner
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  • #1
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Hello. I'm looking for a quad op amp similar to TL074 but rail to rail (mainly for input) in DIP14 (I found a lot in SMD) and supporting +12V / -12V as power supply.
 

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  • #3
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Thanks but I'm looking for DIP14 package not SMD
 
  • #4
jim hardy
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Thanks but I'm looking for DIP14 package not SMD
OOPS !
Haste makes waste - i looked at this and just saw 14 pins.
upload_2017-12-29_4-55-27.png

my mistake

...http://cds.linear.com/docs/en/datasheet/14901fb.pdf
http://www.ti.com/lit/ds/symlink/lt1014.pdf
both perhaps a bit slow for audio
 

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  • #5
Averagesupernova
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Texas Instruments LMC660 is a rail to rail op amp that I have had ok luck with.
 
  • #6
jim hardy
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What is behind your need for rail to rail input ? Might there be a way around it so you can stick with everyday TLO74?
 
  • #8
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Hi. Sorry LMC660 is limited to +15.5 V power supply and I need -12 -> +12V
 
  • #9
Tom.G
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rail to rail (mainly for input)
I don't think there is such a thing, at least not in bi-polar technology. Consider that the input stage will have an inherent VBE to turn on and that there must be a load for the first stage, in either the Emitter or Collector, to sense the change in current. It might be possible in MOSFET technology with a depletion mode input stage but I haven't thought it through completely. Your best bet is to put a voltage divider in the input to stay within the Common Mode range. You only need to lose 10% to 20% of input range, not a big hit for later gain stages.

Or can you just increase the supply voltage, maybe even with a couple boost-converters?

FURTHER DIGGING:
You may be able to use a couple of MOSFETs as a pre-amp input stage to get close to rail-to-rail input but it seems like a lot of added complexity for little gain.

A Google search shows a few hits for rail-to-rail input but they are low supply voltage (7V), single or dual, and small packages.
https://www.google.com/search?q="op+amp"+depletion+mode+input

Let us know how it turns out.
 
  • #10
davenn
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looking for a quad op amp similar to TL074 but rail to rail (mainly for input)

FURTHER DIGGING:
You may be able to use a couple of MOSFETs as a pre-amp input stage to get close to rail-to-rail input but it seems like a lot of added complexity for little gain.

A Google search shows a few hits for rail-to-rail input but they are low supply voltage (7V), single or dual, and small packages.
https://www.google.com/search?q="op+amp"+depletion+mode+input

you may be on the right track
@Ravaner wasn't really specific in the requirement

does he really mean like this Op-amp ?..... ( referring to the type of input ONLY)

NCS2002 ?

http://www.onsemi.com/pub/Collateral/NCS2002-D.PDF
 
  • #13
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Finally, I found a more or less bad solution with LT1491, which has, unfortenatly, a very short GBWP with 200 kHz. Thanks for all yours replies
 
  • #16
analogdesign
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I don't think there is such a thing, at least not in bi-polar technology. Consider that the input stage will have an inherent VBE to turn on and that there must be a load for the first stage, in either the Emitter or Collector, to sense the change in current. It might be possible in MOSFET technology with a depletion mode input stage but I haven't thought it through completely. Your best bet is to put a voltage divider in the input to stay within the Common Mode range. You only need to lose 10% to 20% of input range, not a big hit for later gain stages.

I know this is an older thread, but in case someone reads it and is interested, you can make rail-to-rail op amps without any technology changes (such as depletion mode devices). The key idea is to put a PNP diff pair in parallel with a NPN diff pair. Then you use an adaptive bias circuit to adjust the currents between the two stages to approximate constant gm from rail to rail. Typically you don't really need to cover both rails, in which case you just need to choose PNP or NPN inputs (or PMOS or NMOS if you're doing a CMOS chip).
 
  • #17
Tom.G
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The key idea is to put a PNP diff pair in parallel with a NPN diff pair.
Interesting approach! I'm interesting in following up on it. Can you point me to a datasheet so I can follow up?
 
  • #18
analogdesign
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Do you have access to the IEEE Journal of Solid-State Circuits? The primary paper is Huijsing and Linebarger, "Low-Voltage Operational Amplifier with Rail-to-Rail Input and Output Ranges", IEEE J. Solid-State Circuits, vol. 20, no 6. December 1985.

The paper would go into a lot of detail. Maxim has an app note the technique. https://www.maximintegrated.com/en/app-notes/index.mvp/id/4428

The Linear Tech LT1366 also uses the technique. There is some info in the datasheet but not a ton. http://cds.linear.com/docs/en/datasheet/1366fb.pdf
 

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