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Entry  Wed Jan 30 14:00:02 2013, Charles, Update, ISS, ISS Design and Prototyping ISS.filISS_Transfer_Function.pngD020241-D2.pdf
    Reply  Wed Jan 30 14:37:01 2013, Zach, Update, ISS, ISS Design and Prototyping Screen_Shot_2013-01-30_at_4.22.46_PM.png
Message ID: 7965     Entry time: Wed Jan 30 14:37:01 2013     In reply to: 7964
Author: Zach 
Type: Update 
Category: ISS 
Subject: ISS Design and Prototyping 

Quote:

Unfortunately, as noted in the file, not all of the elements are possible to analyze in liso, such as any type of op-amp with more than two inputs and one output (AD602 used in this design has 16 pins with two distinct amplifiers contained within).

Typically, you can still find a way to model the important parts of the stages that are not as simply added. In the case of the differential input stage, in particular, it is important to include it because it will usually set the input noise level of the circuit. In this case, the noise is the same as the second stage (U5) and it has a gain of 1, so there is essentially no difference (up to factors of sqrt(2) or 2).

You can edit the opamp.lib file and add in custom components. For the input stage, you can just pretend it is a simple non-inverting amplifier with the specified noise characteristics from the datasheet: un = 1.3n, uc = 50 Hz (see below).

For dual op amps, you can usually just model each part separately. For example, the OPA2604 is a dual op amp that is included in the opamp.lib and can be treated as a single one in a model.

Screen_Shot_2013-01-30_at_4.22.46_PM.png

 

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