Author Topic: What am I doing wrong in ltspice?  (Read 1462 times)

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Offline avogadroTopic starter

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What am I doing wrong in ltspice?
« on: February 13, 2020, 11:36:38 am »
Hello,

Im trying to do AC analysis of CE amplifier in ltspice. Im getting error "Iteration limit reached" when adding resistor between emitter and ground. Im using bi component for current controlled current source with setting I=I(R1)*100. Why is this failing to simulate? Whats the correct way of doing it?

I attached the schematic.
 

Offline Kuba_eM

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Re: What am I doing wrong in ltspice?
« Reply #1 on: February 13, 2020, 11:44:04 am »
Should B1 parameter not be given as {I(R1)*100} ?
 

Offline avogadroTopic starter

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Re: What am I doing wrong in ltspice?
« Reply #2 on: February 13, 2020, 12:07:39 pm »
Should B1 parameter not be given as {I(R1)*100} ?

It works without those curly brackets, the problem is with the resistor R1, without it it works fine. Anyways I got it to simulate for lower values of R1 (like 20 ohm works). I wonder if this has something to do with the settings?
 

Online iMo

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Re: What am I doing wrong in ltspice?
« Reply #3 on: February 13, 2020, 12:10:32 pm »
Post your .asc file..
Readers discretion is advised..
 

Offline avogadroTopic starter

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Re: What am I doing wrong in ltspice?
« Reply #4 on: February 13, 2020, 12:26:08 pm »
 

Offline Wimberleytech

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Re: What am I doing wrong in ltspice?
« Reply #5 on: February 13, 2020, 01:38:56 pm »
For whatever reason, it does not like the I(R1) expression.  Use a voltage source with zero volts instead.

<<update>>
It converges if there is no multiplier while using I(R1).
I have increased the iteration limit to 3000 (with gain of 100) and it still does not converge.
Hmmmmm...
« Last Edit: February 13, 2020, 02:09:18 pm by Wimberleytech »
 

Online iMo

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Re: What am I doing wrong in ltspice?
« Reply #6 on: February 13, 2020, 07:16:52 pm »
Try with current controlled current source.
F1 is the CCCS, controlled by the current flowing via V2, the gain=100.
« Last Edit: February 13, 2020, 07:21:02 pm by imo »
Readers discretion is advised..
 

Offline Wimberleytech

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Re: What am I doing wrong in ltspice?
« Reply #7 on: February 13, 2020, 07:29:48 pm »
Try with current controlled current source.
F1 is the CCCS, controlled by the current flowing via V2, the gain=100.

I concur.  The CCCS worked for me as well.  I suspect that a current source with the directive I=I(V1)*100 will instantiate in the matrix just like and F element would.

I am still puzzled why the original post does not work.
 

Online iMo

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Re: What am I doing wrong in ltspice?
« Reply #8 on: February 13, 2020, 08:28:23 pm »
@Wimberleytech: But you have got a typo in your schematics - the current is I(V2)*100.
I think the F converts differently..
« Last Edit: February 13, 2020, 08:33:57 pm by imo »
Readers discretion is advised..
 

Offline Wimberleytech

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Re: What am I doing wrong in ltspice?
« Reply #9 on: February 13, 2020, 11:24:01 pm »
@Wimberleytech: But you have got a typo in your schematics - the current is I(V2)*100.
I think the F converts differently..
|O oops you are right.  It still converges once I change it to V2.

As far as how the matrix is instantiated...that was just a guess, but an educated one.

When I run them together I get exactly the same result.
 


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