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CACD Group
updated 2000.08.21

Noise Analysis (Simple Example)

Operating point
noise example
.control
noise v(2) v1 lin 8 100kHz 1MegHz 2
.endc
v1 1 0 dc 700mV ac 1V
i1 1 2 dc 10mA ac 50mA
r1 1 2 1
d1 2 0 diode
.model diode d rs=10m tt=5us kf=1f
.end

Linearised ac circuit


Note, that ac magnitude of the input source has to be one.

Thermal noise of the resistors r1 and rs given by: Shot and flicker noise of the diode d1 given by: All independent sources eliminated (set to zero), noise generators added




Noise analysis creates two plots named noise1 and noise2. The first one contains the information about noise spectral densities, and the second about total noises. The vectors in noise1 are: onoise_r1 =
      
onoise_d1_rs =
      
onoise_d1_id =
      
onoise_d1_1overf =
      
onoise_d1 = onoise_d1_rs + onoise_d1_id + onoise_d1_1overf
onoise_spectrum = onoise_r1 + onoise_d1
inoise_spectrum = onoise_spectrum / |A|2The vectors in noise2 are:
onoise_total_r1 =
onoise_total_d1_rs =
onoise_total_d1_id =
onoise_total_d1_1overf =
onoise_total_d1 =
      onoise_total_d1_rs + onoise_total_d1_id + onoise_total_d1_1overf
onoise_total = onoise_total_r1 + onoise_total_d1
inoise_total_r1 =
inoise_total_d1_rs =
inoise_total_d1_id =
inoise_total_d1_1overf =
inoise_total_d1 =
      inoise_total_d1_rs + inoise_total_d1_id + inoise_total_d1_1overf
inoise_total = inoise_total_r1 + inoise_total_d1
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