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Transfer Function solution

Forum|Forum|4 years ago
July 1, 2021
6 replies
36860 views

I am trying to find Transfer function for the variables Rc1, Rc2, Rc3 and Rc4 but the tool runs into runtime error . Basically, I need transfer function in terms of Rc1, Rc2,Rc3 and Rc4.

EDIT : attached the worksheet. Now, I am getting out of memory as error.

1_Cal_bioZ.zip

Best answer by -MFra-

We like precise and clear questions. Yours is very cryptic, devoid of data. Questions like that just waste us time.

M

mvenich

14-Alexandrite

Post the full Mathcad worksheet please. Don't expect people to type in the equations for you.

R

RY_8246596

Author

1-Visitor

Edited and updated in the original post .Thanks

ttokoro

21-Topaz I

t.t.

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-MFra-

21-Topaz II

As it is written, the system is in 6 equations and eleven unknowns. If you define five of the unknowns and give initial estimates for the remaining six unknowns, you can get a result. The result sought can be obtained by simple inspection of the circuit assuming as output a and b.

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-MFra-

21-Topaz II

Using the scheme: "Given .... Find(....)", being known the values of the constants and the initial estimates of the unknowns, you get only numerical results. Since you do not provide numerical values for constants or initial estimates, it is assumed that you are looking for a symbolic solution. The transfer function is defined as the ratio between an output quantity and the system's input quantity. Considering the voltage between a and b as the output quantity, and the current Is as the input quantity, it results that the transfer function is a trans- resistance.
One way to go is by using the network topology as follows (see attached photo -the verses of the currents in the graph are random):

Answer to RY_8246596.jpg Answer to RY_8246596+1.jpg

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-MFra-

21-Topaz II

Inspection solution:

Answer to RY_8246596+2.jpg

R

RY_8246596

Author

1-Visitor

Basically, the Va and Vb nodes go into InAmp in the real real circuit. The whole thing is differential. It's part of MAX30001 IC the Va and Vb are BIP and BIN pins of the IC and Is is the current generator across DRVP and DRVN nodes. My intention is to find Transfer function interms of Rc1---Rc4 and later determine the sensitivity of Rc1--Rc4 to Rx and Ry. The, Ra, Rb, Rc and Rd are representing voltage controlled switches which i modelled here as resistances to realize the combinations 0000---1111 for the circuit but now i could see that the Ra-Rd can't be substituted to infinity to represent open switch(0). But, I am getting some sense from your suggestion for the context of my original post.

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-MFra-

Answer

21-Topaz II

We like precise and clear questions. Yours is very cryptic, devoid of data. Questions like that just waste us time.

L

LucMeekes

23-Emerald IV

Your problem is simple, clear from that start (not at all cryptic), and your mistake is obvious.

You have 6 equations, so at best you can solve for 6 variables. I guess they would be the 6 V-terms (Va through Vq). That means adding Rc1 through Rc4 to the Find() statement should result in an error message.

Here is how it can be done: