OPA637: Gain Bandwidth Product

[FAE] Andrew Wang

Genius 10685 points

Part Number: OPA637
Other Parts Discussed in Thread: OPA627

Hi Team,

Customer is asking why GBP (80MHz) of OPA637 list in the datasheet does not correlate with our graphs?

The best I can tell is just about 60MHz.

How to read GBP from the graph then? Please kindly educate, thanks!

Andrew

over 7 years ago

0 Marek Lis over 7 years ago

TI__Guru 71711 points

Andrew,

For decompensated amplifiers like OPA637, where a second pole occurs before zero-crossing, the gain-bandwidth Product (GBP) is different than a Unity-gain Bandwidth (UGB). For that reason, you must look at the bandwidth for close-loop gains higher than 1 - see below.

For example, for close-loop gain of 1000 (Gcl=60dB), the effective bandwidth is 60kHz so the GBP=Gcl*60kHz=1000*60kHz=60MHz - see above.

0 [FAE] Andrew Wang over 7 years ago in reply to Marek Lis

TI__Genius 10685 points

Hi Marek,

Thanks for teaching!!
So why we specify 80MHz as GBP in OPA637 datasheet?
Andrew

0 Marek Lis over 7 years ago in reply to [FAE] Andrew Wang

TI__Guru 71711 points

Andrew,

Judging by the fact that for G=10 (20dB) the graph show close-loop bandwidth of 5MHz (thus, GBP=10*5MHz=50MHz) while the datasheet table lists it as 80MHz, I believe OPA637 AOL vs frequency graph is simply inaccurate and would trust the GBP of 80MHz number ( decompensated from OPA627 by the factor of 5). Having said that, this is only a typical value that may change over process variations by as much as +/-30%; therefore, the actual GBP may in some wafer lots be as low as 56MHz or as high as 104MHz.

0 [FAE] Andrew Wang over 7 years ago in reply to Marek Lis

TI__Genius 10685 points

You are the man as always. =O

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OPA637: Gain Bandwidth Product