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Steve Taranovich

The Diamond Plot

Steve Taranovich
etnapowers
etnapowers
7/8/2014 6:04:58 AM
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Newbie
Re: Saturation
That's correct, the saturation has to be accurately simulated by designers that have not only to simulate the effect of the  variation of parameters like temperature, voltage and current but also the worst case scenarios in terms of drift of the parameters (montecarlo simulations) and load-line variation

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DaeJ
DaeJ
7/7/2014 9:41:29 PM
User Rank
Master
Re: Saturation
Saturation point (SP) limits the circuit, and defines partially product electric characteristics. Saturation could be defined by each component as well as the integrated system. SP could be slightly different among each component. To investigate SP, designer checks these parameters: temperature; current; and voltage.

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steve.taranovich
steve.taranovich
7/2/2014 11:05:05 PM
User Rank
Blogger
Re: The plot thickens
@vasanjk----I was "bitten" by this kind of design oversight in my early design years, but Burr-Brown engineers stressed the Common mode plot to me when I worked for them. There was even a program on TI which is a rollover from Burr-Brown that can tell you if your input signals are going to be a problem---you insert your design criteria and the INA part number and it will let you know if there will be a problem.

 

I can't seem to find it, but you can ask TI apps on the E2E community

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vasanjk
vasanjk
7/2/2014 12:36:57 PM
User Rank
Master
The plot thickens
Steve

I never understood the importance of the "plot" before reading this blog. If the signal input amplitudes are sufficiently small and as long as the used gain factors do not throw the output to the rail, for example in case of patient monitoring like ECG and EEG, the plot goes unnoticed.

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etnapowers
etnapowers
7/1/2014 12:04:37 PM
User Rank
Newbie
input and output impedance
The input impedance of these amplifiers should be as high as possible, ideally infinite, to decouple the amplifier from the input source, and for the same reason the output impedance should be as low as possible, ideally zero.

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etnapowers
etnapowers
7/1/2014 11:36:47 AM
User Rank
Newbie
CMRR
"these linear devices amplify the voltage difference between their inputs, independent of the input voltage relative to the supply voltage. The input common-mode voltage, which is the average of the two input voltages, is rejected by the amplifier."

The CMRR (Common Mode Rejection Ratio) is the parameter utilized to describe the quality of an amplifier, being the ratio between the amplification factor of the differential mode voltage and the amplification factor of the common mode voltage.

Ideally the CMRR should be  as big as possible.

 

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etnapowers
etnapowers
7/1/2014 5:54:56 AM
User Rank
Newbie
Saturation
"The problem is sometimes accurately explained as "the output is saturated," but other times the description can be a little more cryptic: "the gain error is very high," or "the amplifier is very nonlinear," or simply "it doesn't work when it should." We don't have a flow chart to solve customer problems, but if we had one, "check the diamond plot" would come right after "make sure the part is powered up."

Among the possible reasons for the saturation of the output there is also the load variation: a load that requires a different power amount due to , for example, a degradation of its leakage current, may saturate the output when the load driving capability is overpassed.

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