--- In LTspice@..., "ingodettmann <ingod@y...>"
<ingod@y...> wrote:
Hi everbody,
does anyone know, how I can add a noise source in a transient
simulation (if it is possible at all)?
I tried to modell a noise source with a behavioral voltage source
but i didn't work.
Hello Ingo,
there is a very easy way to make such a noise source.
Firstly we should be aware that the rand() funktion has equal
probability for every voltage level between 0 and 1.
This is not like a gaussian noise where you have higher values with
lower probabilty. I remembered a theorem that the generated noise
becomes more gaussian by adding many such noise sources.
I have preferred three sources.
Example:
Digital noise clock is 1e4Hz. "time" is the keyword for time in
the .tran analysis. You can use it in your B-sources.
You have to increase the rand() frequency 1e4 to your requirements.
I think that the offset parameter in the rand() function should be
increased proportionally to the frequency. The intention of this
offset parameter is to make the three rand() functions more like
independant noise sources.
Best Regards
Helmut
Example; f=1.0e4
B1: V=2*rand(time*1e4)
B2: V=2*rand(time*1e4+0.0911e4)
B3: V=2*rand(time*1e4+0.2131e4)
.tran 0 100m 0 10u
Example; f=1.0e9
B1: V=2*rand(time*10e9)
B2: V=2*rand(time*10e9+0.0911e9)
B3: V=2*rand(time*10e9+0.2131e9)
.tran 0 1u 0 0.1n
netlist
-------
*
B1 N001 0 V=2*rand(time*1e9+0.2131e9)
B2 N002 N001 V=2*rand(time*1e9+0.0911e9)
B3 N003 N002 V=2*rand(time*1e9)
R1 N003 out 50
C1 out 0 1p
.tran 0 1u 0 0.1n
.backanno
.end
Schematic
---------
SHEET 1 912 712
WIRE 192 80 192 32
WIRE 192 208 192 160
WIRE 192 -96 192 -48
WIRE 192 -176 192 -224
WIRE 192 -224 464 -224
WIRE 544 -224 576 -224
WIRE 576 -224 576 -192
WIRE 576 -128 576 -96
FLAG 192 208 GND
FLAG 576 -96 0
FLAG 576 -224 out
SYMBOL BV 192 64 R0
SYMATTR InstName B1
SYMATTR Value V=2*rand(time*1e9+0.2131e9)
SYMBOL bv 192 -64 R0
SYMATTR InstName B2
SYMATTR Value V=2*rand(time*1e9+0.0911e9)
SYMBOL bv 192 -192 R0
SYMATTR InstName B3
SYMATTR Value V=2*rand(time*1e9)
SYMBOL res 448 -208 R270
WINDOW 0 32 56 VTop 0
WINDOW 3 0 56 VBottom 0
SYMATTR InstName R1
SYMATTR Value 50
SYMBOL cap 560 -192 R0
SYMATTR InstName C1
SYMATTR Value 1p
TEXT 192 -256 Left 0 !.tran 0 1u 0 0.1n
