Circuit Basics

Understanding Components

GEEC provides a comprehensive library of electrical components commonly used in circuit design and analysis.

Component Categories

Basic Components

These are the fundamental building blocks of circuits, shown directly in the Components section of the left menu:

Sources

Provide electrical energy to circuits (found in the Categories section):

Dependent Sources

Sources whose output depends on another circuit quantity:

Semiconductor Devices

Non-linear components for active circuits:

• Diode — One-way current flow
• BJT Transistor — Bipolar junction transistor
• MOS Transistor — Field-effect transistor
• Operational Amplifier — High-gain differential amplifier

Two-Port Elements

Complex circuit models:

• Transmission Line — High-frequency distributed element
• Transformer — Coupled inductors for impedance matching
• Subcircuit — Reusable custom multi-element block

Drawing Circuits

Placing Components

1. Select a component from the left menu (either Components or Categories)
2. Click on the canvas where you want to place it
3. The component appears with its default orientation
4. Right-click the placed component to open its properties

Orienting Components

After placing or selecting a component, you can change its orientation using keyboard shortcuts or the Tools tab in the top bar:

Drawing Wires

Wires connect component terminals and form circuit paths:

1. Press W or click Wire in the left menu
2. Click a component terminal (the small filled dot at the end of each pin)
3. Click another terminal or point on the canvas to end the segment; right-click to cancel the current segment without leaving the wire tool

Wire behaviors:

• Snap to terminals — Wires automatically connect when their endpoint lands on a component terminal
• Orthogonal routing — Wires travel horizontally or vertically only; they never run at arbitrary angles
• Node naming — Right-click a wire or terminal to open the Rename Node dialog and give that net a meaningful name (e.g., out, Vcc); named nets appear in analysis signal selectors

Drawing Lines and Text

Use annotation tools for labels, arrows, and decorative lines. All drawing tools are in the Drawing section of the left menu:

Component Properties

Each component has a set of properties that control its simulation behavior and appearance.

Accessing Properties

Right-click any component on the canvas to open its properties dialog directly. The dialog contains:

The Properties table lists every parameter defined for that component type. Each row has four columns:

Using Expressions as Values

Any property Value field accepts a symbolic expression instead of a plain number:

R             # Design variable named R
R*2           # Expression referencing a variable
1/(2*Pi*f*C)  # Frequency-dependent formula

See Interactive Features for how to set numeric values for design variables and use interactive sliders.

Editing Circuits

Selecting Items

Moving Items

1. Click and drag any selected item; all selected items move together
2. Items snap to the grid when released; toggle the grid in the bottom bar (press G) to control snapping

Copying and Pasting

Deleting Items

Select item(s) and press Delete or Backspace. Wires connected exclusively to the deleted component are removed automatically.

Modifying Wires

Changing wire routing direction: Double-click a wire segment to toggle its routing axis (horizontal ↔ vertical).

Renaming a net: Right-click a wire or terminal to open the Rename Node dialog. All terminals sharing that net are renamed together. If you type an existing node name, the two nets merge.

Repositioning a wire: Click a point where two wire segments meet (a waypoint) and drag it to reroute.

Circuit Layout Best Practices

Readability

• Logical flow — Arrange components left-to-right or top-to-bottom following signal flow
• Spacing — Leave room between components for clarity
• Alignment — Use the grid to keep things aligned
• Named nodes — Label key nets (in, out, Vcc, GND) for use in analysis expressions

Netlist Generation

GEEC generates a netlist automatically from the canvas. To inspect it, open the Export tab in the top bar and choose Spice or Symbolic under the NetList section. The netlist is displayed in a dialog and can be copied to the clipboard.

Component Alternations

Many components offer multiple symbol variants (alternations) — for example, European vs. US resistor symbols, or different capacitor styles:

• Double-click a component to cycle through its alternations
• Press A to do the same from the keyboard

The active alternation can also affect which properties and netlist template are used for that component.

Visibility and Display Options

Control what labels are shown on the canvas via the Tools tab in the top bar:

Grid spacing is controlled in the bottom bar: the first number is the grid step size; the second (Show each) controls how many grid lines apart one visible line is drawn.

Ready for analysis? Continue to Analysis Guide to learn how to simulate your circuits.