125 lines
4.5 KiB
Plaintext
125 lines
4.5 KiB
Plaintext
ANALYSES
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========
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This file lists the analyses currently implemented into ngspice.
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Table of Contents
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1 Noise analysis (NOISE)
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1.1 Small signal noise
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1.2 Transient noise
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2 Operating point analysis (OP)
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3 Operating point sweep Analysis (DC)
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4 Pole-zero analysis (PZ)
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5 Small-Signal distortion analysis (DISTO)
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6 Small Signal frequency response analysis (AC)
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7 Sensitivity analysis (SENS)
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8 Transfer function analysis (TF)
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9 Transient analysis (TRAN)
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10 Periodic steady state analysis (PSS, experimental feature)
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11 S-parameter analysis (SP)
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1 Noise analysis (NOISE)
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1.1 Small signal noise
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The noise analysis does analysis device-generated noise for the given
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circuit. When provided with an input source and an output port, the analysis
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calculates the noise contributions of each device (and each noise generator
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within the device) to the output port voltage. It also calculates the input
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noise to the circuit, equivalent to the output noise referred to the
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specified input source. This is done for every frequency point in a specified
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range - the calculated value of the noise corresponds to the spectral density
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of the circuit variable viewed as a stationary gaussian stochastic process.
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1.2 Transient noise
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Time domain noise analysis during transient simulation is enabled by
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providing voltage (and current) source options with white, 1/f and
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random telegraph signal noise signals.
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2 Operating point analysis (OP)
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The operating point analysis determines the dc operating point of the
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circuit with inductors shorted and capacitors opened. If a simple matrix
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solution fails, two versions of gmin stepping may be followed by source
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stepping and finally an OP search by a transient simulation.
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3 Operating point sweep Analysis (DC)
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The operating point sweep analysis determines the values of output
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variables while one or two specified independent voltage or current source is
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stepped over a user-specified range and the dc output variables are stored
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for each sequential source value. Resistance and temperature sweep are
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included.
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4 Pole-zero analysis (PZ)
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The pole-zero analysis computes the poles and/or zeros in the small-signal
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ac transfer function. The program first computes the dc operating point and
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then determines the linearized, small-signal models for all the nonlinear
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devices in the circuit. This circuit is then used to find the poles and zeros
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of the transfer function. Unfortunately this code is (since its inception in
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spice3) not free of bugs.
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5 Small-Signal distortion analysis (DISTO)
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The distortion analysis computes steady-state harmonic and intermodulation
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products for small input signal magnitudes. Not all devices are supported.
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6 Small Signal frequency response analysis (AC)
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The ac small-signal computes the ac output variables as a function of
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frequency. The program first computes the dc operating point of the circuit
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and determines linearized, small-signal models for all of the nonlinear
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devices in the circuit. The resultant linear circuit is then analyzed over a
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user-specified range of frequencies.
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7 Sensitivity analysis (SENS)
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Ngspice will calculate either the DC operating-point sensitivity or the AC
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small-signal sensitivity of an output variable with respect to all circuit
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variables, including model parameters. Spice calculates the difference in an
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output variable (either a node voltage or a branch current) by perturbing
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each parameter of each device independently.
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8 Transfer function analysis (TF)
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The (small signal) transfer function analysis computes the dc small-signal
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value of a transfer function (ratio of output variable to input source),
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input resistance, and output resistance is also computed as a part of the dc
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solution.
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9 Transient analysis (TRAN)
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The transient analysis computes the transient output variables as a
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function of time over a user-specified time interval. The initial conditions
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are automatically determined by a dc analysis. All sources which are not time
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dependent (for example, power supplies) are set to their dc value.
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10 Periodic steady state analysis (PSS)
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The periodic steady state analysis computes solutions for oscillating
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circuits. Currently only the autonomous case is implemented.
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11 S-parameter analysis
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Evaluate S parameters on any port of a multiport circuit, store the resulting
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data in a Touchstone file
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Load S parameters from s2p file into code model, and do ac simulation on an
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automatically generated lumped element circuit.
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