Name: diode reverse current and breakdown
Uploaded: 2024-07-08T13:20:19.000Z
Duration: 1 min 14 s
Channel: JoVE

A diode is reverse-biased when its n-type region is connected to the positive terminal of the supply voltage and its p-type region is connected to the negative terminal.
At lower reverse bias voltages, the small leakage current through the diode is primarily due to minority carriers, and the IV curve in this region is almost flat.
As the reverse bias voltage increases beyond a threshold voltage, known as the breakdown voltage or the knee voltage, a steep rise in the current is observed for a small variation in the voltage.
In heavily doped diodes at high reverse voltages, the electric field across the depletion region is strong enough for the valence electrons to break free from their bonds. This creates electron-hole pairs, resulting in a significant increase in current.
In lightly doped diodes, high reverse voltages accelerate the minority carriers across the depletion region. They collide with atoms, creating additional electron-hole pairs. This process cascades, leading to a rapid increase in current.
In lightly doped diodes, the current increases gradually compared to the heavily doped diodes.

diode: reverse bias

A diode is reverse-biased when the positive terminal of an external voltage source is connected to the n-type material and the negative terminal to the p-type material. This configuration opposes the natural direction of current flow through the diode, effectively increasing the width of the depletion region and the barrier potential. The reverse bias condition produces a minimal leakage current, primarily due to minority charge carriers. This leakage becomes significant when the reverse voltage surpasses the thermal voltage under standard room conditions, leading to a flattened current-voltage (I-V) response curve. Unlike the exponential current increase observed in forward bias, the increase in reverse bias is negligible.
However, in practice, the reverse current in diodes often exceeds the predicted saturation current. For instance, diodes designed for small signals with femtoampere-level reverse saturation currents may exhibit nanoampere-level reverse currents. While this reverse current slightly increases with the reverse voltage, these changes are too small to affect the I-V curve noticeably. This reverse current originates from thermal carrier generation within the junction, depending on the diode junction's physical dimensions.
A sharp increase in reverse current occurs when the applied reverse voltage reaches a critical threshold known as the breakdown voltage, specific to each diode. This phenomenon, represented by the knee on the I-V curve, signifies a substantial current rise with minimal voltage increase.
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It's essential to recognize that diode breakdown is not inherently damaging, provided the current stays within its safe operating area, typically defined by its maximum power dissipation capacity in the datasheet. External circuitry, designed to limit reverse current to safe levels, is necessary to prevent potential damage. Zener diodes, engineered to function within the breakdown region for voltage regulation, exemplify diodes that operate safely under these conditions.

Diode: Reverse bias

A diode is reverse-biased when its n-type region is connected to the positive terminal of the supply voltage and its p-type region is connected to the ...

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Electrical Engineering

Unit 1

Diodes

KEY TERMS AND CONCEPTS

diode reverse current and breakdown

A diode in reverse bias blocks current flow and widens its depletion region. In this setup, the positive terminal of the power source connects to the n-type material, and the negative terminal connects to the p-type material. The reverse connection also raises the barrier potential, so current stays very small.

The small reverse current is called leakage current. It comes mainly from minority charge carriers. At room temperature, once the reverse voltage is above the thermal voltage, the diode’s I-V curve becomes nearly flat, unlike the steep rise seen in forward bias.

Real diodes often show more reverse current than the ideal saturation current predicts. Small-signal diodes with femtoampere-level reverse saturation current may still measure nanoampere-level reverse current. This current can rise a little as reverse voltage increases, but the change is usually too small to affect the I-V curve much. It comes from thermal carrier generation in the junction and depends on the junction’s physical size.

A sharp increase in reverse current begins at the breakdown voltage. This is the critical reverse voltage where the I-V curve shows a knee and current rises quickly with little extra voltage. Breakdown is not always damaging if the current stays within the diode’s safe operating area, which is usually tied to the maximum power dissipation listed in the datasheet. External circuitry is used to keep reverse current safe, and Zener diodes are designed to work in the breakdown region for voltage regulation.

Diode Reverse Current and Breakdown

the ideal diode

Ideal Diode I-V Curve and Rectification

An ideal diode is a simple model of a semiconductor diode used to show how current moves through circuits. A diode has two terminals. The anode is positive, and the cathode is negative. In this model, current can flow only in one direction. When a positive voltage is applied to the anode relative to the cathode, the diode is forward-biased. In that state, it conducts current. When the cathode is at a higher potential than the anode, the diode is reverse-biased. It then blocks current and acts...

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A diode in reverse bias blocks current flow and widens its depletion region. In this setup, the positive terminal of the power source connects to the n-type material, and the negative terminal connects to the p-type material. The reverse connection also raises the barrier potential, so current stays very small. The small reverse current is called leakage current. It comes mainly from minority charge carriers. At room temperature, once the reverse voltage is above the thermal voltage, the...

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modeling of diode reverse characteristics

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Zener diode load-line modeling shows how a reverse-biased diode sets a steady voltage in a circuit. Zener diodes use reverse breakdown in a controlled way, so they can hold a fixed voltage across their terminals. This makes them useful for voltage regulation. When the reverse voltage rises above the Zener voltage, or VZ, the diode enters the breakdown region. In this region, the current-voltage, or I-V, curve becomes nearly vertical after the knee current, IZ, is reached. That means the...

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key terms and concepts

Learn how reverse bias creates leakage current, why the diode I-V curve flattens, and what happens at breakdown voltage, including safe use in Zener diodes.

Diode Reverse Current and Breakdown | JoVE K12

JoVE Core Electrical Engineering offers easy-to-understand animated videos that cover fundamental concepts of electric circuits along with circuit analysis techniques. It incorporates first-order and second-order circuits using operational amplifiers and circuit transformation concepts. The inclusion of practical design examples and real-world applications through scientist-in-action videos adds significant educational value, making complex concepts accessible.

electrical engineering

Diode Reverse Current and Breakdown

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