Schottky Diode Symbol
Definition: The Schottky Diode symbol represents a metal-semiconductor junction diode with a lower forward voltage drop (typically 0.15–0.45 V) and faster reverse recovery than a standard p-n junction diode, drawn as a triangle (anode) pointing to a vertical bar (cathode) whose ends curl into small horizontal S-shaped hooks — the distinctive Schottky symbol per IEC 60617-05 and ANSI/IEEE 315 — with two terminals: Anode and Cathode.
Also known as: Schottky barrier diode, hot-carrier diode, metal-semiconductor diode, SBD, fast diode.
What the Schottky Diode symbol means
The Schottky Diode symbol in a circuit diagram represents a rectifying junction formed between a metal (typically titanium or molybdenum silicide) and n-type semiconductor, rather than the p-n semiconductor junction of a conventional diode. This metal-semiconductor Schottky barrier produces a lower forward voltage drop (VF ≈ 0.15–0.45 V vs 0.6–0.7 V for silicon p-n diodes) and an extremely fast reverse recovery time (near zero — essentially no minority carrier storage), making Schottky diodes the preferred choice for high-frequency and power-efficient rectification.
In schematics, the Schottky diode symbol indicates a rectifying element chosen specifically for its low VF (to minimise power loss in the conducting direction) or for its near-instantaneous switching speed (to prevent reverse-conduction during high-frequency switching cycles). The symbol is immediately distinguished from a standard diode by the distinctive curled cathode bar ends.
How to identify the Schottky Diode symbol
The Schottky Diode symbol consists of a triangle with its apex touching a vertical line (the same base structure as a standard diode), but the vertical cathode bar has both ends bent into small S-shaped or backwards-S-shaped hooks — one curling upward and one curling downward. The Anode pin connects to the left (the flat base of the triangle) and the Cathode pin connects to the right (the curled bar). Current flows from Anode to Cathode in the forward direction. The curled ends on the cathode bar are the sole visual distinction from a standard rectifier diode symbol.
Function in a circuit
A Schottky diode conducts current from anode to cathode when the anode voltage exceeds the cathode by approximately 0.15–0.45 V (the Schottky barrier potential), compared to 0.6–0.7 V for silicon p-n diodes. Because the Schottky barrier is a metal-semiconductor junction, there is no minority carrier injection and therefore no reverse recovery time — the diode switches from conducting to blocking essentially instantaneously when the anode voltage drops below the cathode. In reverse bias, the diode blocks current up to its reverse breakdown voltage (typically 20–200 V for general-purpose types). The combination of low VF and zero reverse recovery makes Schottky diodes essential in switch-mode power supplies, high-frequency rectifiers, and OR-ing diodes.
Standards: IEC vs ANSI
| IEC 60617 | IEC 60617-05 defines the Schottky diode symbol as the standard diode symbol (triangle to bar) with S-shaped hooks on both ends of the cathode bar. The IEC reference for Schottky diodes is within section 05 (semiconductors) of IEC 60617. |
|---|---|
| ANSI/IEEE 315 | ANSI/IEEE 315-1975 (and IEEE 315A-1986) defines the same Schottky diode symbol: a triangle pointing to a bar with small S-shaped curls on both ends of the cathode bar. The symbol is identical in IEC and ANSI representations. |
| Key difference | The Schottky diode symbol is identical in IEC 60617-05 and ANSI/IEEE 315. Both use the triangle-to-curled-bar representation. The IEC and ANSI standards differ in some diode variants (e.g., Zener bar style) but are consistent for the Schottky symbol. |
Terminals / pins
| Pin | Name |
|---|---|
| anode | Anode |
| cathode | Cathode |
Typical values
Forward voltage (VF): 0.15–0.25 V for Ge-equivalent small-signal types; 0.35–0.45 V for general-purpose Si types at rated current. Reverse breakdown voltage (VR): 20 V to 200 V typical; high-voltage types to 1200 V (SiC Schottky). Reverse recovery time (trr): effectively 0 ns (no minority carrier storage). Maximum forward current: 1 A to 400 A (power types). Junction capacitance: 0.5–10 pF (small-signal). Operating temperature: −65 °C to +125 °C.
Where the Schottky Diode symbol is used
- Switch-mode power supply (SMPS) output rectifiers — eliminating reverse recovery loss in buck, boost, and flyback converters at switching frequencies above 100 kHz
- OR-ing diodes in redundant power supply systems — two power supplies each connected through a Schottky diode to a common bus with minimal forward-voltage power loss
- Reverse-polarity protection — a Schottky diode in series with the supply input blocks reverse voltage with only 0.3 V forward drop when correctly polarised
- Logic-level clamping — Schottky-clamped transistors (as in STTL logic) where a Schottky diode from base to collector prevents transistor saturation and speeds switching
- RF envelope detectors — the near-zero reverse recovery allows the diode to rectify RF signals up to GHz frequencies
- Solar panel bypass and blocking diodes — minimising power loss in photovoltaic series strings where low VF is critical for energy harvest efficiency
Example
In a 12 V to 5 V synchronous buck converter, the Schottky Diode symbol shows the Anode connected to the converter's switching node (inductor bottom) and the Cathode connected to GND; during the MOSFET dead-time when both switches are off, the inductor current free-wheels through the Schottky diode with only 0.35 V drop and zero reverse recovery, allowing the converter to operate efficiently at 500 kHz switching frequency without shoot-through or reverse recovery losses.
Key facts
- The Schottky diode symbol is identical in IEC 60617-05 and ANSI/IEEE 315: a triangle pointing to a vertical bar whose ends curl into small S-shaped hooks at both ends of the cathode bar.
- Forward voltage drop for silicon Schottky diodes is 0.15–0.45 V depending on current and type, compared to 0.6–0.7 V for standard silicon p-n diodes — the lower VF reduces conduction power loss by 50–75%.
- Reverse recovery time (trr) is essentially zero for Schottky diodes because the metal-semiconductor junction stores no minority carriers; standard p-n silicon diodes have trr of 50–3000 ns, causing significant switching losses at high frequencies.
- Silicon carbide (SiC) Schottky diodes extend the voltage range to 650–1700 V with trr ≈ 0, enabling high-efficiency rectification in EV chargers, solar inverters, and industrial power supplies operating at 600–1500 V DC.
- The reverse leakage current of Schottky diodes is higher than standard p-n diodes (10–1000 µA vs 10–100 nA), and leakage increases significantly with temperature — a practical limitation for high-temperature applications.
- Reference designator for Schottky diodes in schematics is D followed by a number (e.g., D1, D2); type-specific annotations 'BAT54' (dual Schottky) or '1N5819' are written beside the symbol to identify the specific device.
- The Anode pin connects to the triangle base (p-side equivalent) and the Cathode to the curled bar (n-side equivalent); conventional current flows anode-to-cathode in forward bias, identical to a standard diode.
Frequently asked questions
What does the Schottky diode symbol mean in a circuit diagram?
The Schottky diode symbol represents a metal-semiconductor rectifying diode with a lower forward voltage drop (0.15–0.45 V) and essentially zero reverse recovery time compared to a standard silicon diode. In a circuit, it indicates a diode chosen for high-frequency switching efficiency or minimal forward-voltage power loss.
What does the Schottky diode symbol look like?
The Schottky diode symbol is a triangle (anode, left) pointing to a vertical bar (cathode, right) with small S-shaped hooks curling at both ends of the cathode bar — one hook bends upward, one bends downward. This curled cathode bar is the sole visual distinction from a standard rectifier diode symbol, which has a plain straight bar.
What is the difference between a Schottky diode and a regular diode?
A Schottky diode uses a metal-semiconductor junction (not p-n) giving 0.15–0.45 V forward drop (vs 0.6–0.7 V) and zero reverse recovery time (vs 50–3000 ns for p-n diodes). The trade-off is higher reverse leakage current and lower reverse breakdown voltage. Schottky diodes are preferred for high-frequency and high-efficiency circuits.
How do I identify the anode and cathode of a Schottky diode?
In the Schottky diode symbol, the Anode is the flat base (left side) of the triangle, and the Cathode is the curled bar (right side). Current flows from anode to cathode in forward bias. On a physical diode package, the cathode is typically marked by a band or stripe on the body, identical to a standard diode marking convention.
What is the forward voltage of a Schottky diode?
Silicon Schottky diodes have a forward voltage of approximately 0.15–0.25 V at low currents (small-signal types) and 0.35–0.45 V at rated current (power types). At 1 A, a typical 1N5819 Schottky diode has VF ≈ 0.6 V — still lower than a 1N4001 standard diode at 1 A (VF ≈ 1.0 V). Forward voltage decreases slightly with increasing temperature.
What standard defines the Schottky diode symbol?
Both IEC 60617-05 (semiconductor symbols) and ANSI/IEEE 315-1975 define the Schottky diode symbol as a triangle-to-bar diode symbol with S-shaped curls at both ends of the cathode bar. The symbols are identical in both standards.
What is the reference designator for a Schottky diode?
Schottky diodes use the reference designator D (for diode) followed by a number, such as D1 or D2, in schematics. No separate designator distinguishes a Schottky from other diode types — the device type is identified by the Schottky symbol shape and the part number annotation (e.g., 1N5819, BAT54, MBRS360) next to the symbol.
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