.NOISE |

Noise Analysis

The noise analysis does analysis device-generated noise for the given circuit. When provided with an input source and an output port, the analysis calculates the noise contributions of each device (and each noise generator within the device) to the output port voltage. It also calculates the input noise to the circuit, equivalent to the output noise referred to the specified input source. This is done for every frequency point in a specified range - the calculated value of the noise corresponds to the spectral density of the circuit variable viewed as a stationary gaussian stochastic process.

After calculating the spectral densities, noise analysis integrates these values over the specified frequency range to arrive at the total noise voltage/current (over this frequency range). This calculated value corresponds to the variance of the circuit variable viewed as a stationary gaussian process.

.NOISE V(<node_out> [,node_ref]) <source> <sweep type> <points> <start frequency> <end frequency> [PTS_PER_SUMMARY] |

V(node_out <,node_ref>)

node_out is the node at which the total output noise is desired; if node_ref is specified, then the noise voltage V(node_out) - V(node_ref) is calculated. By default, node_ref is assumed to be ground.

source

Is the name of an independent source to which input noise is referred.

sweep type

Must be LIN, OCT, or DEC, as described below.

Sweep type | Description |

LIN | Linear sweep. The frequency is swept linearly from the starting to the ending frequency. The points is the total number of points in the sweep. |

DEC | Sweep by decades. The frequency is swept logarithmically by decades. The points is the number of points per decade. |

OCT | Sweep by octaves. The frequency is swept logarithmically by octaves. The points is the number of points per octave. |

points

Specifies the number of points in the sweep, using an integer.

start frequency

Is the starting frequency.

end frequency

Is the final frequency.

PTS_PER_SUMMARY

Is an optional integer; if specified, the noise contributions of each noise generator is produced every PTS_PER_SUMMARY frequency points.

The noise analysis produces two plots - one for the Noise Spectral
Density curves and one for the total Integrated Noise over the specified
frequency range. All noise voltages/currents are in squared units (V^{2}/Hz
and A^{2}/Hz for spectral density, V^{2} and A^{2}
for integrated noise).

```
.NOISE V(5) VIN DEC 10 1kHZ 100Mhz
.NOISE V(5,3) V1 OCT 8 1.0 1.0e6 1
```