# IEC tunnel diode: tunnel diode

Canonical URL: https://eloragrid.ai/symbols/iec-tunnel-diode-tunnel-diode
Publisher: Elora Grid
Updated: 2026-10-28
Lookup label: TUNNEL
Drawing use: Schematic
Reference families: IEC, Manufacturer

## Symbol convention

Convention: IEC
Form: Tunnel Diode
Autodesk IEC-60617 Symbol Preview: Semiconductor Components, HDI1_S00645 / VDI1_S00645. This identifies the publisher's library context; exact IEC graphics and database identities are not asserted.

Tunnel diode form: Tunnel Diode.

## In plain English

### What does IEC tunnel diode: tunnel diode mean?

A tunnel diode has a heavily doped junction whose current-voltage characteristic includes a negative differential-resistance region caused by tunnelling. This entry identifies the tunnel diode form in the publisher's IEC-context family.

### A simple example

An oscillator or fast switching circuit can bias the junction in the required region. The bias network is essential to understanding why this device behaves differently from a normal rectifier. 

### What the drawings help you do

A tunnel diode is distinct from a Zener diode: the useful characteristic is its negative-resistance region rather than a specified reverse breakdown clamp.

### This particular reference

Tunnel diode form: Tunnel Diode. This entry adds the tunnel diode detail to the broader tunnel diode family. A tunnel diode is distinct from a Zener diode: the useful characteristic is its negative-resistance region rather than a specified reverse breakdown clamp.

### Terms

- Rating: A value stating the conditions for which equipment is specified.
- Schematic: A drawing showing function and connections rather than physical appearance.

Concept diagram: Identify the device and form → Read the connections and state → Check the equipment reference
A guide to reading this reference. The original symbol illustration and its drawing notes appear below; these boxes are not a wiring diagram.

- [AutoCAD Electrical: Semiconductor components](https://help.autodesk.com/cloudhelp/2021/ENU/AutoCAD-Electrical/files/GUID-AC954072-7314-4682-88AF-38160D61E9A2.htm)


## What it represents

A tunnel diode has a heavily doped junction whose current-voltage characteristic includes a negative differential-resistance region caused by tunnelling. This entry identifies the tunnel diode form in the publisher's IEC-context family.
An oscillator or fast switching circuit can bias the junction in the required region. The bias network is essential to understanding why this device behaves differently from a normal rectifier. 
A tunnel diode is distinct from a Zener diode: the useful characteristic is its negative-resistance region rather than a specified reverse breakdown clamp.

## How to read it

- An oscillator or fast switching circuit can bias the junction in the required region. The bias network is essential to understanding why this device behaves differently from a normal rectifier.
- A tunnel diode is distinct from a Zener diode: the useful characteristic is its negative-resistance region rather than a specified reverse breakdown clamp.

## Information to show or reference

- Identify terminal polarity and the required bias region.
- Reference the selected component characteristics and package pinout.
- Show the surrounding bias and signal-conditioning network.

## Important distinction

This entry adds the tunnel diode detail to the broader tunnel diode family. A tunnel diode is distinct from a Zener diode: the useful characteristic is its negative-resistance region rather than a specified reverse breakdown clamp.

## Facts

- Drawing form: Tunnel Diode
- Public vendor block names: HDI1_S00645 / VDI1_S00645. Autodesk identifiers, not standards database IDs.
- Drawing purpose: tunnel diode
- Graphic scope: Independently authored educational illustration; not certified standard geometry, a terminal pinout or a product footprint.

## Public references

- [AutoCAD Electrical: Semiconductor components](https://help.autodesk.com/cloudhelp/2021/ENU/AutoCAD-Electrical/files/GUID-AC954072-7314-4682-88AF-38160D61E9A2.htm) — Autodesk. Public Semiconductor Components table explicitly lists HDI1_S00645 / VDI1_S00645 with this operating or connection form. Vendor graphics are linked, not copied.

## Graphic scope

Independent original educational concept illustration by Elora Grid. Not a certified standards graphic or manufacturer footprint. Unitless; not to scale. Original artwork licence: https://creativecommons.org/licenses/by/4.0/. Publisher material is linked only.