Basic Analyses (Detailed)
This page provides detailed coverage of basic analysis. Back to Analysis Guide for overview.
Result Analyses
Result analyses return a table of values (voltages, currents, symbolic expressions) directly inside their dialog. There is one dialog per analysis type - running the same type again re-uses the existing dialog.
OP numeric
Computes DC operating point. No configuration needed - GEEC automatically determines node voltages and branch currents. The result table shows:
- Node voltages (e.g.,
v(1),v(out)) - Current through each voltage source (e.g.,
I(V1)) - Additional component-specific results (e.g., power dissipated in resistors)
OP semi-symbolic
Computes DC operating point symbolically with numeric values substituted for design variables marked Use in semisymbolic. Useful when you want simplified formulas instead of raw symbols.
OP symbolic
Fully symbolic DC operating point. Every component value remains as a symbol. Results are algebraic expressions showing how node voltages depend on all component parameters.
AC numeric
Computes AC frequency response at a single frequency. Returns complex phasor values (magnitude + phase) for each selected output variable.
AC semi-symbolic
AC frequency response with numeric design-variable substitution. Returns partially simplified transfer functions.
AC symbolic
Fully symbolic AC analysis. Returns the transfer function H(j?) as an exact algebraic expression in terms of all component values and angular frequency ?.
TF semi-symbolic
Semi-symbolic transfer function H(s) - Laplace-domain representation with some values substituted.
TF symbolic
Fully symbolic transfer function H(s). Ideal for deriving design equations and understanding circuit topology.
Transient semi-symbolic
Semi-symbolic time-domain response using Laplace transform inversion. Numeric design-variable values are substituted before inversion.
Transient symbolic
Fully symbolic transient response - exact closed-form time-domain expression y(t).
Graph Analyses
Graph analyses produce draggable result windows containing an interactive chart. Each click on a graph analysis button in the Analysis tab creates a new named graph window.
DC (DC Sweep)
Sweeps a DC variable across a range and plots the circuit response.
Configuration:
| Field | Description |
|---|---|
| Sweep | Variable to sweep (e.g., voltage source V1, resistor R1) |
| From | Starting value |
| To | Ending value |
| Step | Increment per data point |
| Hysteresis | (not implemented yet) When enabled, performs the sweep in both directions (forward and backward); useful for circuits with hysteretic behavior |
| Parameter | Optional parametric sweep (see Parametric Sweep) |
| X-axis | Variable plotted on the horizontal axis (part of graph configuration) |
| Y-axis | Variable(s) plotted on the vertical axis (part of graph configuration) |
AC/TF (Frequency Response/Transfer Function)
Produces frequency-domain graphs (Bode plots, pole-zero maps, time-domain impulse response).
The graph type is selected via a drop-down inside the dialog:
Frequency response
| Field | Description |
|---|---|
| Frequency variable | Use angular frequency ? or ordinary frequency f |
| Sweep type | Logarithmic (dec), Linear, or Octave |
| Start frequency | Lower limit of frequency sweep |
| Stop frequency | Upper limit of frequency sweep |
| Points | Number of points per decade (log/octave) or total points (linear) |
| Parameter | Optional parametric sweep (see Parametric Sweep) |
| View type | Magnitude + Phase, Magnitude only, Phase only, Real/Imaginary, etc. |
| Y-axis | Output variable(s) to plot (part of graph configuration) |
Time response
Computes the circuit's impulse or step response from the symbolic transfer function.
| Field | Description |
|---|---|
| Impulse type | Heaviside (step), Dirac (impulse), or All (both) |
| From | Start time |
| To | End time |
| Step | Time step |
| Transfer function | Expression for transfer function |
Parameter sweep
Frequency response at a fixed frequency while sweeping a circuit variable.
| Field | Description |
|---|---|
| Frequency | Fixed frequency for the analysis |
| Sweep variable | Which component value or variable to vary |
| Sweep type | Linear, Logarithmic, or Octave |
| From | Start value |
| To | End value |
| Points | Number of points per decade (log/octave) or total points (linear) |
| View type | Magnitude + Phase, Magnitude only, etc. |
| Y-axis | Output variable(s) to plot (part of graph configuration) |
Pole-zero
Maps poles and/or zeros of the circuit transfer function in the complex s-plane.
| Field | Description |
|---|---|
| Output type | Numeric or Symbolic computation |
| PZ type | Pole-zero (both), Poles only, or Zeros only |
| Parameter | Optional parametric sweep (see Parametric Sweep) |
| Transfer function | Expression for transfer function |
Phasors
Plots the phasor representation of voltages/currents at a specific frequency.
| Field | Description |
|---|---|
| Frequency | Fixed frequency for the analysis |
| Phasor variables | Which voltages/currents to plot as phasors |
Transient
Simulates the circuit's time-domain response.
| Field | Description |
|---|---|
| From | Start time (usually 0) |
| To | End time of simulation |
| Step | Time step (smaller = more accurate, slower) |
| UIC | User Initial Conditions - when checked, uses component initial conditions (IC= value) instead of computing a DC operating point at t=0 |
| Parameter | Optional parametric sweep (see Parametric Sweep) |
| X-axis | Variable on horizontal axis (usually time) (part of graph configuration) |
| Y-axis | Output variable(s) to plot (part of graph configuration) |
Parametric Sweep
Most graph analyses support a Parameter sweep that runs the analysis multiple times with a component or design variable stepped over a range, producing a family of curves on a single graph.
Enabling a Parameter Sweep
- In the graph dialog, check the Parameter checkbox
- Enter a sweep expression in the field. Syntax:
variableName=lin(start, stop, count) # Linear sweep
variableName=log(start, stop, count) # Logarithmic sweep
variableName=[val1, val2, val3, ...] # Explicit list of values
Examples:
R1=lin(100, 10000, 5) # Sweep R1 from 100? to 10k? in 5 steps
C1=log(1e-9, 1e-6, 10) # Sweep C1 from 1nF to 1�F logarithmically
R1=[100, 1000, 10000] # Sweep R1 at exactly these three values
- A calculator button (gear icon) next to the field opens an interactive helper for building sweep expressions.
Tips
After enabling a parametric sweep the graph shows one curve per parameter value, each in a different color.
Next: Go to Other Analyses to learn about FFT and Fourier analysis.
Back: Return to Analysis Guide for overview.