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Why do some op amps have a higher GBW than what the unity gain-bandwidth is?

Michael Weaser

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This is mainly a question about the tl074 Operational amplifier and its specifications on its datasheet. Looking on its datasheet its GBW is higher than the listed unity-gain bandwidth. The Unity-gain bandwidth is listed as 3 Mhz , while its GBW is 5.25 Mhz . I thought GBW and unity-gain bandwidth was actually the same thing and I do know of various op-amps that the GBW and the unity-gain bandwidth is the same value. So why do some op-amps have a higher GBW that its unity-gain bandwidth value?
 

KlausST

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Hi,

Unity gain bandwidth and GBW are (almost) equal on a first oder filter characteristic (20dB / decade).
But often there is a second order filter characteristic that starts at a higher frequency (resulting in 40dB/decade).

After this second frequency the GBW and unity gain frequency will differ.

Maybe there are other reasons...
Like In a real circuit ghe slew rate will limit the upper frequency, too, but also depends on amplitude.

Klaus
 
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    d123

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Easy peasy

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where do you get 5.25MHz from .. ? the best part of the graph appears to be 100v/mV x 30kHz = 3MHz ...
 
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LvW

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Yes - I agree wth the explanation as given by KlausST.
Comment: Such opamps (with GBW>unity gain frequency) are NOT unity gain stable.
 
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Michael Weaser

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where do you get 5.25MHz from .. ? the best part of the graph appears to be 100v/mV x 30kHz = 3MHz ...
On page 15 of the tl074 datasheet , at the bottom of the page, under Frequency Response , it says the GBW is 5.25 Mhz , unless it is a typo on the page, as on other websites that just list the specs , also say the GBW is 3 Mhz and not 5.25 Mhz

If you go to Ti's website and view the tl074 : https://www.ti.com/product/TL074 ; It also says the GBW is 3 Mhz, So maybe the datasheet does have a typo?
 
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sutapanaki

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From the right top corner plot Fig.26 on page 27 it seems the UGBW is around 5MHz, so probably as they list 5.24MHz. Then if they also measure the loop gain in an inverting unity gain configuration, the UGBW will be 2x smaller. I look at the Fig.27 and there they show the closed-loop frequency response for gain = 1 and gain=-1 and the one for -1 drops at around 3MHz or maybe slightly below.
 

Audioguru

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Its "typical" unity-gain-bandwidth is 3Mhz so some are lower and others are higher.
It is an AUDIO opamp so it works well to 100kHz. It is not used for radio frequencies.

My datasheet for the TL07xx is dated July 2017. How old is your datasheet?
 

Easy peasy

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You need to read more closely - the "H" version has the higher gain-BW product, the others are 3MHz ...
 

Audioguru

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The datasheet for the "H" version of the TL07x is only less than 2 months old.
I wonder if it is the Toshiba Japanese made version that was "improved" but oscillated and all were recalled.
 

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has it been recalled? - I do not see any on Octopart - a pity since the H version is intended to be the faster version - presumably with less internal compensation - or picked at testing -
 

dick_freebird

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UGBW is difficult to test well on ATE, even
more so at probe. Often this would be a
GNT param, and part acceptance would
use a correlated proxy such as slew rate.

I wonder whether mass market consumer op
amps see packaged test at all, anymore.
Many sub-$/part products that run big volume
don't even probe every die and if yield on what
-is- probed is below par, they just scrap the
wafer before any more money goes into it.

This might be a fly in the "bin it out for higher
price" ointment, even if the part is capable.
 

Audioguru

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has it been recalled? - I do not see any on Octopart - a pity since the H version is intended to be the faster version - presumably with less internal compensation - or picked at testing -
Lots of companies make TL07x ICs but the one from Toshiba a few years ago had an oscillation problem because they made it "better".
Texas Instruments recently began making the H version.
 

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