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ANALYSES
========
This file lists the analyses currently implemented into ngspice.
Table of Contents
1 Noise analysis (NOISE)
1.1 Small signal noise
1.2 Transient noise
2 Operating point analysis (OP)
3 Operating point sweep Analysis (DC)
4 Pole-zero analysis (PZ)
5 Small-Signal distortion analysis (DISTO)
6 Small Signal frequency response analysis (AC)
7 Sensitivity analysis (SENS)
8 Transfer function analysis (TF)
9 Transient analysis (TRAN)
10 Periodic steady state analysis (PSS, experimental feature)
1 Noise analysis (NOISE)
1.1 Small signal noise
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.
1.2 Transient noise
Time domain noise analysis during transient simulation is enabled by
providing voltage (and current) source options with white, 1/f and
random telegraph signal noise signals.
2 Operating point analysis (OP)
The operating point analysis determines the dc operating point of the
circuit with inductors shorted and capacitors opened.
3 Operating point sweep Analysis (DC)
The operating point sweep analysis determines the values of output
variables while one or two specified independent voltage or current source is
stepped over a user-specified range and the dc output variables are stored
for each sequential source value. Resistance and temperature sweep are
included.
4 Pole-zero analysis (PZ)
The pole-zero analysis computes the poles and/or zeros in the small-signal
ac transfer function. The program first computes the dc operating point and
then determines the linearized, small-signal models for all the nonlinear
devices in the circuit. This circuit is then used to find the poles and zeros
of the transfer function. Unfortunately this code is (since its inception in
spice3) not free of bugs.
5 Small-Signal distortion analysis (DISTO)
The distortion analysis computes steady-state harmonic and intermodulation
products for small input signal magnitudes. Not all devices are supported.
6 Small Signal frequency response analysis (AC)
The ac small-signal computes the ac output variables as a function of
frequency. The program first computes the dc operating point of the circuit
and determines linearized, small-signal models for all of the nonlinear
devices in the circuit. The resultant linear circuit is then analyzed over a
user-specified range of frequencies.
7 Sensitivity analysis (SENS)
Ngspice will calculate either the DC operating-point sensitivity or the AC
small-signal sensitivity of an output variable with respect to all circuit
variables, including model parameters. Spice calculates the difference in an
output variable (either a node voltage or a branch current) by perturbing
each parameter of each device independently.
8 Transfer function analysis (TF)
The (small signal) transfer function analysis computes the dc small-signal
value of a transfer function (ratio of output variable to input source),
input resistance, and output resistance is also computed as a part of the dc
solution.
9 Transient analysis (TRAN)
The transient analysis computes the transient output variables as a
function of time over a user-specified time interval. The initial conditions
are automatically determined by a dc analysis. All sources which are not time
dependent (for example, power supplies) are set to their dc value.
10 Periodic steady state analysis (PSS)
The periodic steady state analysis computes solutions for oscillating
circuits. Currently only the autonomous case is implemented.
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