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ANALYSES
========

This file lists the analyses currently implemented into ngspice.

Table of Contents

 1 Noise analysis (NOISE) 
 2 Operating point analysis (OP)
 3 Operating point sweep Analysis (DC)
  3.1 Enhancements
 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)



1 Noise analysis (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.
 

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.

 3.1 Enhancements
  
  Added resistance and temperature sweep.


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. 


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. 


