Possible competition for the LTC2057?

[DiligentMinds.com]

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[Andreas]

Hello Ken,

depends on what parameters you are after.
Yes the specs look good.

But like the LTC2057 the input bias current is relatively high.
And current noise is relatively high on the ADA.
So you are limited to input impedances lower than about 10-100k.

With best regards

Andreas

[Kleinstein]

It depends on the application which AZ OP fits. One parameter is the size of the input stage. This is a balance between bias current and noise. Low noise types generally have higher bias currents.  So the ADA4522 is more on the side of very low noise, but high bias. The LTC2057 still has significant bias - about half of the ADA4522. There are also types with much lower Bias but than more noise.

So there is not 1 good AZ OP to fit all needs.

The rather unique feature of the LTC2057 is the high working voltage, especially as LTC2057HV.  There are not many alternatives at the high voltage. The AD4822 is one, especially at low source impedance.

The high voltage low noise types have an additional problem: they get relatively warm und thus thermal design gets more important.

[tszaboo]

I think it is similar to the ADA4638. That one also has bullshit overshoot with very minimal capacitive load. 20% with 100pF while the LTC has less than 5%.

[dom0]

Well it only has a typical 69° phase margin at unity gain and that will go down even further when loading it stronger (especially considering the somewhat high closed-loop output impedance of 340 ? in the unity loop gain region!), so, not really surprising.

[Mickle T.]

I think it is similar to the ADA4638. That one also has bullshit overshoot with very minimal capacitive load. 20% with 100pF while the LTC has less than 5%.

ADA4638 is a totally different beast.  LTC2057 have bullshit EMIRR.

[tszaboo]

Well it only has a typical 69° phase margin at unity gain and that will go down even further when loading it stronger (especially considering the somewhat high closed-loop output impedance of 340 ? in the unity loop gain region!), so, not really surprising.

I was able to make the ADA4638 oscillate by loading it with some PCB trace, some components, cable and a DMM. Wasnt very happy about it. Especially that we were replacing them by hand on so many units due to a deadline.