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Help with LTSpice Op-Amp Modelling

noobeestudent

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Hello guys, I'm in need of urgent help.

For my assignment, I was required to model an Op-Amp using a Behavioral Voltage Source using LTSpice.
The input resistance of the Op-Amp is 70MΩ and output resistance is 30Ω. The open loop voltage gain is 80k and the supply voltages is +-15V. I'm having problems with the behavioral voltage source. This is what I got so far.1603015225516.png
Can anyone help me? Thank you in advance.
 

FvM

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E.g. :

1603019101849.png

By the way, did you study the behavioral OP models shipped with LTspice, ipamp, opamp2 and universalopamp2?
 

noobeestudent

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Thanks for the help.
By the way, did you study the behavioral OP models shipped with LTspice, ipamp, opamp2 and universalopamp2?
I did learn to use those but I was asked to use the behavioral voltage to model the op-amp in this assignment
 

noobeestudent

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I need help again. I am supposed to use the above op-amp model to create a non-inverting amplifier with a gain of 40.
1603113687205.png
This is what I have now. But the syntax for the behavioural voltage source does not work. What does it need to be?

Edit: Ive figured it out, changed it to "V=limit((V(Vi)-V(Vx))*80k,-15,15)" and it worked.
 
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FvM

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There's a nice online help, why don't you read it?

Wrong node voltage syntax, write either V(Vi,Vx) or (V(Vi)-V(Vx)).
 

noobeestudent

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Using this op-amp model , i have to integrate these extra conditions
  • Unity gain bandwidth = 10MHz
  • Frequency response roll-off rate = 20 dB/dec

1603119175456.png

Does anyone knows how to implement those into the op amp model?
Any help is very much appreciated. Thanks a lot.
 

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