Name: zener diode load-line modeling
Uploaded: 2024-07-08T13:20:20.000Z
Duration: 1 min 14 s
Channel: JoVE

ダイオードの逆特性をモデル化するには、逆バイアスされたダイオード回路を調べる必要があります。
ツェナーダイオード回路が、所望の出力電圧に一致するブレークダウン電圧を備えているとします。
ダイオードは、逆電圧がブレークダウン電圧を超えるとブレークダウン領域に入ります。
電流-電圧特性曲線は、ニー電流を超える電流の垂直直線に近似しています。
キルヒホッフの電圧法則を使用して、ダイオード電流、ソース電圧、およびダイオード電圧降下の関係を確立する数式を推論できます。
この関係は、負荷線と呼ばれる直線としてグラフィカルに表されます。
負荷線がダイオード曲線と交差する点(点Qで示される)は、回路の動作点を示します。
ツェナーダイオードのデータシートには、ブレークダウン電圧、ニー電流、インクリメント抵抗、および電力定格が記載されています。
ツェナーダイオードの電力定格は、ツェナーダイオードを損傷することなく、ツェナーダイオードを流れる可能な最大電流を計算するのに役立ちます。

ダイオードの逆特性のモデリング

電子回路では、逆バイアスダイオード構成が電圧レベルの調整に重要です。ツェナーダイオードは逆ブレークダウン現象を利用し、特定のツェナー電圧 (V_Z) で制御されたブレークダウンを示します。端子間の電圧を一定に保つように設計されており、回路の電圧調整によく使用されます。

ツェナーダイオードに印加される逆電圧がブレークダウン電圧を超えると、ダイオードはブレークダウン領域に入ります。この時点で、ダイオードの電流-電圧 (I-V) 特性曲線は、膝電流 (I_Z) と呼ばれる特定のしきい値を超える電流に対して実質的に垂直になります。
キルヒホッフの電圧則は、ソース電圧、ダイオードの電圧降下、およびダイオード電流の間の数学的関係を提供するのに役立ちます。これは負荷線によってグラフィカルに表され、回路内のダイオードのすべての可能な平衡点を示します。負荷線とダイオードの特性曲線の交点は、定常動作点 Q を示します。
膝電流を超える電流では、ツェナーダイオードの電圧は安定しており、電流がさらに増加し てもほとんど変化しません。この安定性は、動作点での曲線の傾きの逆数として定義されるダイオードの増分抵抗の結果です。したがって、ダイオード全体の電圧変動は、増分抵抗と膝電流を超える電流に比例します。ツェナーダイオードは、さまざまな電流範囲にわたって一定の電圧を維持できるため、安定した基準電圧を作成し、過電圧状態から回路を保護するのに非常に役立ちます。
製造者は、ツェナーダイオードの逆ブレークダウン電圧、膝電流、増分抵抗、および電力定格を提供しています。電力定格により、ツェナーダイオードを損傷することなく流れる最大電流を推定できます。

ダイオードの逆特性をモデル化するには、逆バイアスされたダイオード回路を調べる必要があります。
ブレークダウンを持つツェナーダイオード回路を考えてみましょう...

modeling-of-diode-reverse-characteristics

Education

JoVE Core

Electrical Engineering

電気工学

Unit 1

ユニット1

Diodes

ダイオード

KEY TERMS AND CONCEPTS

主要用語と概念

Modeling of Diode Reverse Characteristics

zener diode load-line modeling

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 voltage changes very little even if the current keeps increasing.

Kirchhoff’s voltage law helps connect the source voltage, diode voltage drop, and diode current. The result is a load line, which shows the possible operating points in the circuit. Where the load line crosses the diode curve is the steady-state Q point.

Above the knee current, the diode’s small voltage change is linked to its incremental resistance. Incremental resistance is the reciprocal of the curve slope at the operating point. The voltage variation across the diode depends on this resistance and on the current above IZ.

Zener diodes are valuable because they provide stable reference voltages and help protect circuits from overvoltage. Manufacturers list the reverse breakdown voltage, knee current, incremental resistance, and power rating. The power rating also helps estimate the maximum current the diode can carry without damage.

Zener Diode Load-Line Modeling

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...

diode: forward bias

Diode Current in Forward Bias

Diode current in forward bias depends on how the p-type and n-type regions are connected to a battery. When the p-type region is tied to the positive terminal and the n-type region to the negative terminal, the diode is forward-biased. This setup lowers the potential barrier inside the diode and lets current move easily from the p-type side to the n-type side. The current-voltage behavior of a forward-biased diode is described by its I-V characteristics. These characteristics depend on the...

diode: reverse bias

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...

zener diodes

Zener Diode Voltage Regulation

Zener diodes are semiconductor devices used to hold voltage steady in reverse bias. In reverse breakdown, current flows into the cathode and makes it positive relative to the anode. This behavior is different from a conventional diode and is the reason Zener diodes are useful in voltage regulation. A Zener diode has a nearly vertical current-voltage, or I-V, curve above a threshold called the knee current. That shape lets it keep a fairly stable voltage over a wide range of currents.

modeling of diode forward characteristics

modeling-of-diode-forward-characteristics

Diode Forward Bias: I-V Curve and Models

Diode forward bias is analyzed with the current-voltage, or I-V, curve and two common circuit models. These models help describe how a diode behaves when current flows in the forward direction. They are useful for electronic circuit design and analysis. The exponential diode model is used when the source voltage rises above 0.5 volts. At that point, the diode current increases exponentially above the saturation current. The I-V curve shows this nonlinear response as the forward voltage...

small-signal diode model

Diode Bias and Small-Signal Response

Diode bias and small-signal response describe how a diode behaves when a steady DC voltage and a tiny changing signal act on the same circuit. The DC bias sets the diode’s operating point, or Q point. Around that point, the diode current and voltage follow an exponential I-V relationship. A small time-varying signal can be added on top of the DC bias to study how the diode responds to small changes. When the signal voltage is much smaller than the thermal voltage, the diode’s behavior can be...

modeling of diode reverse characteristics

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...

half wave rectifier

Single-Diode AC to DC Conversion

Single-diode AC to DC conversion uses a half-wave rectifier to change alternating current into a unidirectional voltage. The circuit is simple. It uses one diode in series with a load resistor and an AC power source. The diode controls the current because it allows flow in only one direction. During the positive half-cycles of the AC input, the diode is forward-biased. When the input voltage is greater than the diode threshold, current flows and an output voltage appears across the load...

full wave rectifier

AC to DC Conversion with Full-Wave Rectifiers

A full-wave rectifier converts alternating current, or AC, into direct current, or DC. It is more efficient than a half-wave rectifier. The circuit usually uses a center-tapped transformer, two diodes, and a load resistor. The center-tapped transformer is the key part of the circuit. Its secondary winding is split into two equal voltages with opposite polarities. That split lets the rectifier use both halves of the AC input waveform. During the positive half-cycle of the AC signal, diode D1...

bridge rectifier

AC to DC Conversion with Bridge Diodes

A bridge rectifier converts alternating current (AC) into direct current (DC) using four diodes arranged in a bridge layout. It is used to turn both halves of the AC waveform into a single-direction output. That makes it an important part of many electronics circuits. During the positive half-cycle, diodes D1 and D2 conduct. Current then flows through the load resistor R. At the same time, D3 and D4 are reverse-biased, so they do not conduct. The action switches during the negative half-cycle.

clipper circuit

Dual Diode Wave Clipping

Dual diode wave clipping uses diodes and biasing batteries to reshape an AC signal. A clipper circuit is a wave-shaping device that changes waveform parts without changing the whole signal. It is commonly used in television and radar communication systems to improve waveform modulation in transmitters and receivers. A dual-clipper setup uses two ideal diodes, two biasing batteries, and a resistor connected in parallel. The circuit works by responding to the phase of the input AC signal. The...

clamper circuit

DC Restorer for Waveform Level Shifting

A clamper circuit, or DC restorer, shifts a waveform up or down by adding a DC level. It is a special form of rectifier circuit. In this setup, the output is taken across the diode instead of across the capacitor. The circuit works well with square wave inputs and other pulse signals. The diode direction lets the capacitor charge to the most negative peak of the input signal. After that, the diode stops conducting. The capacitor then holds that voltage at a steady value. As a result, the...

voltage doubler circuit

How a Voltage Doubler Raises AC Output

A voltage doubler circuit raises the output voltage by using a clamping section and a rectifier section. The clamping section includes a capacitor, C1, and a diode, D1. The rectifier section includes a second diode, D2, and a capacitor, C2. The circuit starts working when a sinusoidal input signal enters the clamping section. Under ideal conditions, this stage clamps the positive peaks at zero volts. It also lets the negative peak reach a magnitude that is twice the input amplitude. That...

schottky barrier diode

Fast Switching in Schottky Diodes

Schottky barrier diodes use a metal-semiconductor junction to control current flow. They are built by combining a metal layer with a moderately doped n-type semiconductor. This contact creates the Schottky barrier, which gives the diode its one-way current behavior. When the metal touches the semiconductor, charge transfer occurs. The Fermi levels of the two materials align, and a depletion region forms near the contact area. In an n-type semiconductor, this region contains uncompensated...

key terms and concepts

Learn how Zener diodes use reverse breakdown, load lines, and the Q point to keep voltage stable in circuits and protect against overvoltage.

Zener Diode Load-Line Modeling | JoVE K12

JoVE Core 電気工学 は、電気回路の基本概念と回路解析テクニックを網羅したアニメーションビデオシリーズです。オペアンプと回路変換および 1 次・ 2 次回路の概念を網羅しています。実験を撮影した実写動画では、設計例や現代社会での応用が含まれており、複雑な概念も分かりやすく学習いただけます。

electrical engineering

Zener Diode Load-Line Modeling

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