学生党求问LTSPICE做AC分析的问题

IC超级菜鸟

实验要求-3db带宽，但是用.meas命令怎么都搞不出来，照着帮助手册的语法试了好多种还是没改出来，求问是什么问题
.ac oct 10000 100 1e7
.meas AC xx v(out) WHEN v(out)=-3db
显示错误是Measurement "xx" FAIL'ed

IC超级菜鸟

顶一下

IC超级菜鸟

有人知道问题出在哪吗？

peterlin2010

.meas AC xx v(out) WHEN v(out)=-3db



for  hspice
hspice use vdb(out)  

vdb  ,

vp =phase

vm









.meas ac vfbgain   max vdb(vfb1)
.MEAS AC VFBPM FIND PAR('180+vp(vfb1)') WHEN vdb(vfb1)=0
.meas ac vfb1_pm find vp(vfb1) when vdb(vfb1)=0
.MEAS AC GM FIND PAR('0-vdb(vfb1)') WHEN vp(vfb1)=0

IC超级菜鸟

peterlin2010 发表于 2019-4-20 13:47
.meas AC xx v(out) WHEN v(out)=-3db

试了下不行，LTSPICE的语法和HSPICE有点不太一样
Syntax: .MEAS[SURE] [AC|DC|OP|TRAN|TF|NOISE] <name>
+ [<FIND|DERIV|PARAM> <expr>]
+ [WHEN <expr> | AT=<expr>]]
+ [TD=<val1>] [<RISE|FALL|CROSS>=[<count1>|LAST]]

Syntax: .MEAS [AC|DC|OP|TRAN|TF|NOISE] <name>
+ [<AVG|MAX|MIN|PP|RMS|INTEG> <expr>]
+ [TRIG <lhs1> [[VAL]=]<rhs1>] [TD=<val1>]
+ [<RISE|FALL|CROSS>=<count1>]
+ [TARG <lhs2> [[VAL]=]<rhs2>] [TD=<val2>]
+ [<RISE|FALL|CROSS>=<count2>]

.MEAS AC tmp max mag(V(out));

peterlin2010

IC超级菜鸟 发表于 2019-4-20 20:41
试了下不行，LTSPICE的语法和HSPICE有点不太一样
Syntax: .MEAS[SURE] [AC|DC|OP|TRAN|TF|NOISE]
+ [ ]

https://www.electro-tech-online. ... s-error-log.149212/

.meas ac VL12 find V(L1)-V(L2) at=50

The result is given in dB. Unfortunately, I cannot change the axis from log to linear, as I have no axis. I just do the simulation for this single frequency of 50 Hz.

Is it nevertheless possible (and how) to output the wanted voltage in V, not just in dB?