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I want to make capacitor value C1=C2=C3 and change it at once.

I know the .STEP PARAM command, but it needs at least two values.

I want to set all values equal, and change it simultaneously.

Like this. If I do set C=10u, All the capacitor's size is set to 10u. Is there any command or method to realize this?

Voltage Spike
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fluencer
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2 Answers2

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Use the .param command

.param C 10u
Voltage Spike
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    OP, just to be clear: .param sets the value of the parameters (the ones you have enclosed in the curly braces), while .step steps between some values for a parameter. The .step comand doesn't need to have a .param defined elsewhere, that's why it works to have it as standlone. But any value that uses parameters enclosed in curly braces needs to have that parameter defined somewhere. If there is no .step command then a .param must be used. – a concerned citizen Jun 08 '21 at 22:33
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While on the subject of changing parameters, it might be worth mentioning this method described in the question:

How to use .step param with more than two parameters in LTSpiceIV

Basically, the .step directive is used with an index variable and the table() function is used to lookup parameter values based on the index. The example from the above question:

.step param Rx list 1 2 3
.param R1 table(Rx,1,1k,2,1Meg,3,1k)
.param R2 table(Rx,1,10k,2,1Meg,3,10Meg)

This is useful if two or more parameters are not equationally related to each other.

ErikR
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