Name: diode current in forward bias
Uploaded: 2024-07-08T13:20:19.000Z
Duration: 1 min 20 s
Channel: JoVE

다이오드는 p형 영역이 공급 전압의 양극 단자에 연결되고 n형 영역이 음극 단자에 연결될 때 순방향 바이어스됩니다. 
순방향 전류-전압 특성은 0.7V 미만의 바이어스 전압에 대해 무시할 수 있는 전류를 표시하며, 이를 컷인 전압이라고 합니다. 그러나 바이어스 전압이 0.7V를 약간 초과하면 다이오드의 전류가 급격히 상승합니다.
결과적으로 정격 전류가 다른 완전 전도 다이오드는 서로 다른 전류에서 0.7V 강하를 나타냅니다.
다이오드의 전류-전압 관계에는 온도와 단면적에 따라 달라지는 포화 전류가 포함됩니다.
볼츠만 상수와 전자 전하의 크기를 포함하는 열 전압은 온도로 표현됩니다.
상당한 순방향 전류의 경우, 다이오드 방정식은 지수 형태로 단순화되고 열 전압으로 대수적으로 표현됩니다.
두 다이오드 전압에 대한 전류를 비교하면 base-10 로그를 사용하는 방정식은 전류의 10배 변화가 다이오드에서 약 60밀리볼트 전압 강하에 해당함을 나타냅니다.

다이오드: 순방향 바이어스

반도체 소자에서 다이오드는 전류의 흐름을 지시하는 중요한 역할을 하며, 그 동작은 크게 순방향 바이어스와 역방향 바이어스로 구분됩니다. 다이오드의 p형 영역이 배터리의 양극 단자에 연결되고 n형 영역이 음극 단자에 연결되면 다이오드가 순방향 바이어스된다고 합니다. 이 구성은 다이오드 내의 전위 장벽을 줄여 전류가 p형 영역에서 n형 영역으로 쉽게 흐르도록 합니다.
순방향 바이어스에서 다이오드의 동작은 다이오드의 재료, 온도 및 물리적 치수의 영향을 받는 I-V 특성에 의해 결정됩니다. 순방향 바이어스된 경우 다이오드의 전류(I_D)는 다이오드 방정식으로 설명할 수 있습니다.
<img alt="Equation 1" src="/files/ftp_upload/15713/15713_Equation_1.svg" style="height: 26px;">
여기서 I_S는 포화 전류, q는 전자 전하, V_D는 다이오드에 적용된 전압, n은 방출 계수, k는 볼츠만 상수, T는 접합 온도입니다. 열 전압 V_T(kT/q)는 다이오드를 통해 전하 캐리어를 이동하는 데 필요한 에너지를 측정하며 실온에서의 값은 약 26mV입니다.
<img alt="Figure 1" src="/files/ftp_upload/15713/15713_Figure_1.svg" style="height: 200px;">
다이오드는 컷인 전압(실리콘 다이오드의 경우 일반적으로 0.7V) 미만의 전압에 대해 무시할 수 있는 전류를 보여줍니다. 순방향 바이어스에서는 순방향 전류가 10년마다 변경될 때마다 다이오드 전압이 약 60mV씩 변경됩니다. 포화 전류(I_S)는 온도와 다이오드의 단면적에 따라 달라지며 10°C 증가할 때마다 두 배로 증가합니다. I_S와 V_T의 온도 의존성으로 인해 정전류에서 온도가 1°C 증가할 때마다 다이오드의 전압 강하는 약 2mV씩 감소합니다. 이는 전자 온도계와 같은 온도 감지 회로에 활용되는 특성입니다. 이러한 특성을 이해하는 것은 정류기, 신호 혼합기, 전압 조정기와 같이 다이오드가 핵심 구성 요소인 전자 장치에 매우 중요합니다.

다이오드는 p형 영역이 공급 전압의 양극 단자에 연결되고 n형 영역이 공급 전압의 양극 단자에 연결될 때 순방향 바이어스됩니다.

Education

교육

JoVE Core

Electrical Engineering

전기공학

Unit 1

제1단원

Diodes

다이오드

KEY TERMS AND CONCEPTS

주요 용어 및 개념

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 material, temperature, and physical size. The diode current can also be written using the diode equation, which includes saturation current, electron charge, applied diode voltage, emission coefficient, Boltzmann's constant, and junction temperature.

Thermal voltage, written as kT/q, shows the energy needed to move charge carriers across the diode. At room temperature, it is about 26 mV. A silicon diode also shows very little current below its cut-in voltage, which is typically 0.7 V.

In forward bias, the diode voltage changes by about 60 mV for every decade change in forward current. The saturation current changes with temperature and with the diode's cross-sectional area. It doubles for every 10°C increase. Because of the temperature effect on saturation current and thermal voltage, the diode voltage drop falls by about 2 mV for each 1°C rise in temperature at a constant current.

This temperature behavior is useful in circuits that measure heat, such as electronic thermometers. Diodes are also important in rectifiers, signal mixers, and voltage regulators. Understanding forward bias helps explain why diodes are key parts of many electronics.

Diode Current in Forward Bias

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 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

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...

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 a forward-biased diode conducts current, how its voltage changes with current and temperature, and why these properties matter in circuits.

Diode Current in Forward Bias | 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 Current in Forward Bias

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