CCCS (Dependent Current Source) Symbol
Definition: The CCCS symbol represents a current-controlled current source — a dependent source whose output current equals a dimensionless current gain β (A/A) times a controlling current flowing through a designated branch elsewhere in the circuit — drawn per IEEE 315 / ANSI convention as a DIAMOND containing a current-direction arrow, with the controlling branch (Ctrl In, Ctrl Out) carrying the sensed current.
Also known as: current-controlled current source, dependent current source, controlled current source, F source, current amplifier source, current gain source, beta source.
What the CCCS (Dependent Current Source) symbol means
The CCCS symbol denotes an idealized two-port element: a controlling branch (Ctrl In to Ctrl Out) carries a current ix — sensed through ideally zero resistance — and an output port (Out+, Out−) forces a current iout = β·ix regardless of the voltage across it. The gain β (also written F, Ai, or hfe in transistor contexts) is dimensionless, amps per amp, making the CCCS the idealization of a pure current amplifier.
This element is the classic model of bipolar transistor action: in the common-emitter h-parameter model, collector current is hfe times base current — a CCCS with β of 50–500. Current mirrors, Darlington pairs (whose composite gain is roughly β1·β2), and optocoupler current-transfer ratios are all naturally described as current-controlled current sources. In SPICE the CCCS is the F element and, like the CCVS, senses its controlling current through a named voltage source: F1 out+ out− Vsense beta.
How to identify the CCCS (Dependent Current Source) symbol
The output side is a DIAMOND enclosing an ARROW: dependent source (diamond), current output (arrow showing positive current direction). The controlling side is a series branch — Ctrl In and Ctrl Out — through which the controlling current ix flows, with the gain written beside the diamond as β·ix. The combination of internal arrow plus a current in the gain expression uniquely identifies the CCCS among the four dependent sources.
Sort the siblings quickly: arrow inside = current output (F or G); ± inside = voltage output (E or H); ix in the expression = current-controlled (F or H); vx = voltage-controlled (G or E). IEC-tradition schematics may show an annotated circle instead of the diamond, in which case the β·ix annotation is the identifier. In BJT small-signal diagrams the CCCS frequently appears drawn between collector and emitter with the label β·ib.
Live editor identity: Live-library identity: `cccs`, 60 × 60 canvas units, 4 logical terminals. Match this exact SVG and terminal list when identifying the placeable editor symbol; do not identify a physical package from the schematic outline alone.
Function and usage boundary
In analysis the CCCS imposes iout = β·ix, linking two branch currents. Mesh analysis handles it naturally when ix is a mesh current; nodal analysis adds an auxiliary relation expressing ix in terms of node voltages through the element carrying it. The output is an ideal current source (infinite output impedance); the sensing branch is an ideal short (zero voltage drop).
As a device model, the CCCS is the amplifying element of the BJT hybrid model: ic = hfe·ib. It also captures current mirrors (β ≈ 1 from the programming branch to each output leg), Darlington composite gain, and the current-transfer ratio (CTR) of an optocoupler, where the output phototransistor current is CTR times the LED current — a CCCS whose β might be 0.5 to 6 (50–600%).
Usage boundary: Use the CCCS (Dependent Current Source) abstraction only when the intended circuit can be expressed through these logical ports: `out_pos` (Out+), `out_neg` (Out-), `ci` (Ctrl In), `co` (Ctrl Out). Select a versioned physical profile and exact manufacturer datasheet before assigning package pins, ratings, or fabrication dimensions.
Standards: IEC vs ANSI
| IEC 60617 | IEC 60617 does not assign a diamond to dependent sources; strict IEC schematics annotate a circular current-source symbol with the controlling law (β·ix). The diamond remains the dominant convention in textbooks and simulator documentation worldwide. |
|---|---|
| ANSI/IEEE 315 | IEEE 315 / ANSI practice draws the CCCS as a diamond with an internal arrow and the controlling current identified on a designated branch. SPICE implements it as the F element with the controlling current measured through a named voltage source: F<name> out+ out− Vsense gain. |
| Key difference | The visual split is the familiar diamond (IEEE/textbook) versus annotated circle (IEC). As with the CCVS, SPICE requires the controlling current of an F element to flow through a voltage source — a 0 V dummy source if necessary — because branch currents are only observable through voltage sources in the netlist formulation. |
The displayed SVG is the live editor implementation, not a licensed reproduction or certification of an IEC or IEEE database glyph. Verify the exact official entry and project edition before issuing work.
Variant availability
- Editor implementation (available): This is the exact SVG and terminal geometry placed by the CircuitDiagramMaker editor.
- IEC 60617 (reference only): IEC 60617 is the official international source. This page does not present the editor SVG as a licensed or certified IEC reproduction.
- ANSI/IEEE 315 (reference only): IEEE 315 is the North American reference listed by IEEE as inactive-reserved; use the edition required by the project.
Logical terminals
The live editor exposes `out_pos` (Out+), `out_neg` (Out-), `ci` (Ctrl In), `co` (Ctrl Out). These are stable logical terminal IDs for diagram connectivity, not a promise that they equal physical package pin numbers.
| Logical ID | Editor terminal name |
|---|---|
| out_pos | Out+ |
| out_neg | Out- |
| ci | Ctrl In |
| co | Ctrl Out |
Polarity and direction
This editor symbol does not encode a universal positive/negative orientation. Do not infer physical polarity or package pin numbering from left/right placement alone.
Reference designator
Project-defined: No single reference letter is asserted for this broad symbol. Apply the project standard and equipment-classification rules consistently.
Where the CCCS (Dependent Current Source) symbol is used
- BJT small-signal and h-parameter models, where collector current equals hfe (β) times base current
- Current mirror analysis, treating each mirror output as a unity-gain (or ratio-scaled) CCCS of the programming current
- Darlington pair equivalent circuits with composite current gain approximately β1·β2
- Optocoupler models, where output current is the current-transfer ratio (CTR) times LED current
- SPICE behavioral modeling of current amplifiers and current-mode signal processing blocks
- Two-port hybrid-parameter (h-parameter) network representations, whose forward-transfer element hf is a CCCS
Key facts
- The CCCS equation is iout = β·ix; β is a dimensionless current gain in A/A — the same quantity as a BJT's hfe.
- Symbol: diamond (dependent) containing an arrow (current output, direction of positive flow); the controlling current flows in a designated branch (Ctrl In / Ctrl Out).
- SPICE letter F denotes the CCCS in the E/G/H/F scheme; the controlling current must be routed through a named voltage source, e.g. F1 out+ out− Vsense 150.
- The BJT is the canonical CCCS: ic = β·ib is the heart of the transistor hybrid model, with β typically 50–500 for small-signal parts.
- Current mirrors are CCCS elements of gain ≈ 1 (or a designed ratio); Darlington pairs multiply gains for composite β of 1,000–30,000.
- Optocoupler current-transfer ratio (CTR) is a CCCS gain, commonly 50–600%, linking LED current to phototransistor current across galvanic isolation.
- The ideal CCCS senses its control current with zero voltage drop and drives its output with infinite output impedance.
- Dependent sources — the CCCS included — are never zeroed when computing Thevenin/Norton equivalents; only independent sources are killed.
Common interpretation mistakes
- Treating the CCCS (Dependent Current Source) drawing (60 × 60 canvas units) as a physical footprint. The schematic outline expresses electrical intent; package and panel dimensions come from the selected physical profile.
- Copying `out_pos`, `out_neg`, `ci`, `co` directly to a wire marker or manufacturer package pin number. These are logical CCCS (Dependent Current Source) port IDs and require an exact ordered-part terminal map.
- Reversing a polarity-marked CCCS (Dependent Current Source) terminal because the symbol was rotated or mirrored on the sheet.
Frequently asked questions
What is the difference between a CCCS and a VCCS?
Both output a current (diamond with an internal arrow), but the CCCS is controlled by a CURRENT flowing through a branch (iout = β·ix, gain dimensionless A/A), while the VCCS is controlled by a VOLTAGE across two nodes (iout = gm·vx, gain in siemens). The gain expression tells you which: an ix means CCCS, a vx means VCCS. Physically, the CCCS models bipolar transistor current gain; the VCCS models FET transconductance.
Why is the CCCS called the F source in SPICE?
SPICE assigns each dependent source a letter: E (VCVS), G (VCCS), H (CCVS), and F (CCCS). A netlist line beginning with F declares a current-controlled current source, with syntax F1 out+ out− Vsense gain, where Vsense is the name of the voltage source through which the controlling current flows. The letters are historical SPICE conventions rather than initials of the source names.
How does a CCCS model a bipolar transistor?
The defining action of a BJT is current amplification: collector current equals β (hfe) times base current. In the small-signal hybrid model, a CCCS labeled β·ib is drawn from collector to emitter, controlled by the base-branch current. With β = 150, every microamp into the base commands 150 µA of collector current. Adding rπ at the base and ro at the output refines the model, but the CCCS is its amplifying core.
What are the units of CCCS gain?
None — it is a pure ratio, amps out per amp in (A/A). This matches the other dimensionless dependent source, the VCVS (V/V), and contrasts with the VCCS (siemens) and CCVS (ohms). In transistor datasheets the same quantity appears as hFE or β; in optocouplers as CTR, usually quoted as a percentage.
How does SPICE sense the controlling current for an F element?
Through a voltage source. SPICE's formulation only tracks branch currents that flow through voltage sources, so the controlling branch must contain one — if none exists naturally, insert a 0 V dummy source (Vsense a b 0), which acts as a perfect ammeter without affecting the circuit. The F card then references it by name: F1 out+ out− Vsense 100.
Is a current mirror a CCCS?
Functionally, yes. A current mirror copies the current programmed in its reference branch to one or more output branches, which is exactly a CCCS with β ≈ 1 (or a designed ratio, achieved by scaling emitter areas or degeneration resistors). Analyzing a mirror as a unity-gain CCCS with finite output resistance is standard practice for hand calculation of bias networks and active loads.
Sources and verification
- IEC 60617:2026 DB — Graphical symbols for diagrams (International Electrotechnical Commission) — The current official IEC graphical-symbol database and the electrotechnical areas it covers. Exact symbol identity data requires IEC access.; claim scope: standards
- IEEE/ANSI 315-1975 — Graphic Symbols for Electrical and Electronics Diagrams (IEEE Standards Association) — The official catalogue record for North American diagram symbols and reference-designation letters; IEEE lists the standard as inactive-reserved.; claim scope: standards, reference_designator
- IEC 61666:2010+AMD1:2021 — Identification of terminals within a system (International Electrotechnical Commission) — General principles for identifying terminals within systems; it does not replace the exact ordered-device datasheet.
- IEC 81346-2:2019 — Object classes and reference-designation codes (International Electrotechnical Commission) — The official classification scheme used to form reference designations across technical disciplines.; claim scope: reference_designator
- IEC 61082-1:2014 — Preparation of documents used in electrotechnology (International Electrotechnical Commission) — General presentation rules for electrotechnical diagrams, drawings, and tables.; claim scope: standards, usage
Geometry fingerprint: 241177d1fb145cc1. A changed SVG, canvas size, or terminal definition invalidates the recorded review.
Related symbols
- Current Mirror symbol
- Current Source symbol
- Darlington Pair symbol
- NPN Transistor (BJT) symbol
- NPN Transistor symbol
- Optocoupler symbol
Physical breadboard, PCB, and panel mapping
No universal physical profile is published for this symbol yet. Create a versioned custom part from the exact manufacturer dimensions and terminal map before fabrication.
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