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Design >> High-Speed I/O Design >> FASTEST OPAMPS?
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Message started by pavlosEMP on Jul 11^th, 2007, 7:02am

Title: FASTEST OPAMPS?
Post by pavlosEMP on Jul 11^th, 2007, 7:02am

Hello everyone,

I m a new member here, i just came across this forum, and i find it rather useful. To begin with,
does anyone know, what is the most solid criterion to evaluate how fast an opamp is?

I mean is it GBWP, Slew rate,BP? what?

As far as i know it must be GBWP. And if so, what is the highest GBWP of an opamp achieved today, or some list with the opamps having the greater GBWPs?

thanx in advance!

Title: Re: FASTEST OPAMPS?
Post by imtired on Jul 16^th, 2007, 5:43pm

(I am an amateur so please be patient with me if I err in my comments.)

In my mind, fastest means to be able to respond to the input signal and faithfully reproduce it at the output, with or w/o gain. So I would say that slew rate and BW are the main factors in determining the speed of an op-amp. The problem with GBWP is, even though you can have a really large GBWP, it does not mean your BW is high, and often is the case where a really large gain (low BW) is required to maintain stability. Therefore if you have a hgh frequency signal other than a fixed sinusoid, the output waveform will experience distortion due to the early roll-off of a high gain, high GBWP opamp. You'll also have to make sure that your op-amp is capable of driving your load.

Title: Re: FASTEST OPAMPS?
Post by ywguo on Jul 19^th, 2007, 6:46pm

Hi,

It strongly depends on the application. It is more valuable to discuss if you specify where the opamp is used, what the input signal is, etc.

Yawei

Title: Re: FASTEST OPAMPS?
Post by pavlosEMP on Jul 24^th, 2007, 6:13am

The deal here is that, i have developed an algorithm to extract some info which leads me to form an approximation of the impulse response of a circuit, which has a non linear out output.

So by considering a chosen input, we can extract an approximation of the transfer function of the circuit.

The realization of such a circuit, is now a matter of selecting the way to make it, and selecting its components.

I personally, am not in the field of electronics, so all of my colleagues, suggest that i should try a passive realization.

Anyway i have been for quite a while now to find a solution to this problem but i have understood that this impulse response is very very fast indeed, so probably, there aren't any opamps so fast, at least not in the present time.

In the attachement i give to you my impulse response function.
The pairing of the nominators with the denominators, is entirely my arbitrary choice!

Thank you!

Title: Re: FASTEST OPAMPS?
Post by ywguo on Jul 26^th, 2007, 2:45am

Hi,

It seems that it is easier to implement your impulse response function using digital circuit than an opamp. I guess you want to measure the impulse response of a circuitry and extract the transfer function. ::)

Probably what your colleagues recommend is right. Just use a passive circuit like transmission line.

Yawei

Title: Re: FASTEST OPAMPS?
Post by pavlosEMP on Aug 27^th, 2007, 1:45am

thank you very much for your comments!