Name: zener diode voltage regulation
Uploaded: 2024-07-08T13:20:19.000Z
Duration: 1 min 16 s
Channel: JoVE

Al igual que los diodos normales, un diodo Zener permite que la corriente fluya en polarización directa y bloquea la corriente en polarización inversa.
Sin embargo, si el voltaje de polarización inversa excede el voltaje de ruptura inversa del diodo Zener, la corriente fluirá a través de él. El voltaje de ruptura típico para un diodo Zener puede variar desde unos pocos voltios hasta varios cientos de voltios.
En la operación de polarización inversa, particularmente más allá de la corriente de rodilla, el diodo Zener exhibe un comportamiento I-V casi vertical.
A medida que aumenta el voltaje de la fuente, fluye más corriente a través del diodo Zener, pero el voltaje a través de él permanece constante.
La pendiente de las características I-V en polarización inversa se define como el recíproco de la resistencia incremental del diodo Zener.
A medida que la corriente a través del diodo Zener se desvía de su valor especificado, el voltaje a través del Zener varía solo ligeramente. Por lo tanto, los diodos Zener se utilizan como reguladores de voltaje en electrónica sensible.
Sin embargo, esta desviación de voltaje se vuelve más pronunciada cuando la corriente a través del zener se acerca a la corriente de la rodilla, lo que hace que el diodo Zener sea adecuado como regulador de voltaje principalmente en regiones de alta corriente.

diodos zener

Los diodos Zener son dispositivos semiconductores especializados diseñados para funcionar en la región de ruptura inversa, donde permiten que la corriente fluya hacia el cátodo, haciéndolo positivo en relación con el ánodo. Esta operación inversa distingue a los diodos Zener de los diodos convencionales y permite su uso en diversas aplicaciones, sobre todo como reguladores de voltaje. Una de las características que define a los diodos Zener es su curva característica I-V (corriente-voltaje) casi vertical por encima de un cierto umbral de corriente, conocida como corriente de rodilla, que permite al diodo Zener mantener un voltaje relativamente estable en una amplia gama de corrientes.
Los fabricantes especifican la disipación de potencia máxima de un diodo Zener y su voltaje Zener en una corriente de prueba específica. El voltaje Zener, que puede variar desde unos pocos voltios hasta varios cientos de voltios, varía ligeramente con los cambios de corriente. Esta variación se debe a la resistencia dinámica del diodo, definida como la inversa de la pendiente de su curva I-V en la región operativa. Una resistencia dinámica baja es crucial para mantener la estabilidad del voltaje en corrientes variables, lo que mejora la efectividad del diodo Zener en aplicaciones de regulación de voltaje.
Sin embargo, es importante evitar operar diodos Zener en regiones de baja corriente donde su resistencia dinámica aumenta significativamente, ya que esto puede provocar inestabilidad en el voltaje regulado. La dependencia de la temperatura del voltaje Zener es otro factor crítico, ya que el coeficiente de temperatura (expresado en milivoltios por grado Celsius) indica cómo cambia el voltaje con la temperatura. Los diodos Zener de bajo voltaje generalmente exhiben coeficientes de temperatura negativos, mientras que los diodos de alto voltaje tienen coeficientes positivos. Para aplicaciones que requieren un voltaje de referencia estable con una influencia mínima de la temperatura, se puede emparejar un diodo Zener con un coeficiente de temperatura positivo en serie con un diodo conductor directo, compensando efectivamente las variaciones de temperatura.

Diodos Zener

Al igual que los diodos normales, un diodo Zener permite que la corriente fluya en polarización directa y bloquea la corriente en polarización inversa.
Sin embargo, si el voltaje de polarización inversa excede ...

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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. Manufacturers list the Zener voltage at a specific test current and also give the maximum power dissipation.

The Zener voltage can range from a few volts to several hundred volts. It changes slightly as current changes because the diode has dynamic resistance, which is the inverse of the slope of the I-V curve in the operating region. Low dynamic resistance helps the voltage stay stable, so the diode works better as a regulator.

It is important not to run a Zener diode in the low-current region. In that region, dynamic resistance rises a lot and the regulated voltage can become unstable. Temperature also affects Zener voltage, and the temperature coefficient, measured in millivolts per degree Celsius, shows how the voltage changes with temperature.

Lower-voltage Zener diodes usually have negative temperature coefficients. Higher-voltage Zener diodes usually have positive coefficients. For a more stable reference voltage, a Zener diode with a positive temperature coefficient can be connected in series with a forward-conducting diode to help cancel temperature changes.

Zener Diode Voltage Regulation

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 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

Explore how Zener diodes hold voltage steady in reverse breakdown, why dynamic resistance matters, and how temperature affects their use in regulation.

Zener Diode Voltage Regulation | 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

Zener Diode Voltage Regulation

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