Chapter 1: Semiconductor Diodes

Presentación del tema: "Chapter 1: Semiconductor Diodes"— Transcripción de la presentación:

1 Chapter 1: Semiconductor Diodes
Robert Boylestad Digital Electronics Copyright ©2002 by Pearson Education, Inc. Upper Saddle River, New Jersey All rights reserved.

2 Diodes Simplest Semiconductor Device
Slide 1 Diodes Simplest Semiconductor Device It is a 2-terminal device Robert Boylestad Digital Electronics Copyright ©2002 by Pearson Education, Inc. Upper Saddle River, New Jersey All rights reserved.

3 Basic operation Ideally it conducts current in only one direction
Slide 2 Basic operation Ideally it conducts current in only one direction and acts like an open in the opposite direction Robert Boylestad Digital Electronics Copyright ©2002 by Pearson Education, Inc. Upper Saddle River, New Jersey All rights reserved.

4 Semiconductor Materials
Slide 5 Common materials used in the development of semiconductor devices: • Silicon (Si) • Germanium (Ge) Robert Boylestad Digital Electronics Copyright ©2002 by Pearson Education, Inc. Upper Saddle River, New Jersey All rights reserved.

5 Núcleo iónico que consta del núcleo y los electrones interiores
en enlaces covalentes Figura Cristal de silicio intrínseco.

6 libre, pudiendo moverse ambos con libertad por todo el cristal.
Enlace roto Electrón libre Figura La energía térmica puede romper un enlace, creando un hueco y un electrón libre, pudiendo moverse ambos con libertad por todo el cristal.

7 Electrones en enlaces covalentes
Estado vacío (hueco) Electrones en enlaces covalentes Incremento en el tiempo Figura A medida que los electrones se desplazan a la izquierda para llenar un hueco, el hueco se desplaza a la derecha.

8 Electrón de valencia extra del átomo donante Átomo donante Figura El silicio de tipo n se crea añadiendo átomos con impurezas de valencia cinco.

9 Átomo aceptor Enlace vacante que se llena a la temperatura de funcionamiento Figura El silicio de tipo p se crea añadiendo átomos de impureza con valencia tres.

10 Operating Conditions Slide 9 • No Bias • Forward Bias • Reverse Bias
Robert Boylestad Digital Electronics Copyright ©2002 by Pearson Education, Inc. Upper Saddle River, New Jersey All rights reserved.

11 No Bias Condition Slide 10
No external voltage is applied: VD = 0V and no current is flowing ID = 0A. Only a modest depletion layer exists. Robert Boylestad Digital Electronics Copyright ©2002 by Pearson Education, Inc. Upper Saddle River, New Jersey All rights reserved.

12 Reverse Bias Condition
Slide 11 External voltage is applied across the p-n junction in the opposite polarity of the p- and n-type materials. This causes the depletion layer to widen. The electrons in the n-type material are attracted towards the positive terminal and the ‘holes’ in the p-type material are attracted towards the negative terminal. Robert Boylestad Digital Electronics Copyright ©2002 by Pearson Education, Inc. Upper Saddle River, New Jersey All rights reserved.

13 Forward Bias Condition
Slide 12 Forward Bias Condition External voltage is applied across the p-n junction in the same polarity of the p- and n-type materials. The depletion layer is narrow. The electrons from the n-type material and ‘holes’ from the p-type material have sufficient energy to cross the junction. Robert Boylestad Digital Electronics Copyright ©2002 by Pearson Education, Inc. Upper Saddle River, New Jersey All rights reserved.

14 Forward Bias Voltage Slide 16
The point at which the diode changes from No Bias condition to Forward Bias condition happens when the electron and ‘holes’ are given sufficient energy to cross the p-n junction. This energy comes from the external voltage applied across the diode. The Forward bias voltage required for a • Silicon diode VT  0.7V • Germanium diode VT  0.3V Robert Boylestad Digital Electronics Copyright ©2002 by Pearson Education, Inc. Upper Saddle River, New Jersey All rights reserved.

15 Actual Diode Characteristics
Slide 13 Actual Diode Characteristics Note the regions for No Bias, Reverse Bias, and Forward Bias conditions. Look closely at the scale for each of these conditions! Robert Boylestad Digital Electronics Copyright ©2002 by Pearson Education, Inc. Upper Saddle River, New Jersey All rights reserved.

16 Temperature Effects Slide 17
As temperature increases it adds energy to the diode. It reduces the required Forward bias voltage in Forward Bias condition. It increases the amount of Reverse current in Reverse Bias condition. It increases maximum Reverse Bias Avalanche Voltage. Germanium diodes are more sensitive to temperature variations than Silicon Diodes. Robert Boylestad Digital Electronics Copyright ©2002 by Pearson Education, Inc. Upper Saddle River, New Jersey All rights reserved.

17 Diode Specification Sheets
Slide 22 Diode Specification Sheets Data about a diode is presented uniformly for many different diodes. This makes cross-matching of diodes for replacement or design easier. 1. VF, forward voltage at a specific current and temperature 2. IF, maximum forward current at a specific temperature 3. IR, maximum reverse current at a specific temperature 4. PIV or PRV or V(BR), maximum reverse voltage at a specific temperature 5. Power Dissipation, maximum power dissipated at a specific temperature 6. C, Capacitance levels in reverse bias 7. trr, reverse recovery time 8. Temperatures, operating and storage temperature ranges Robert Boylestad Digital Electronics Copyright ©2002 by Pearson Education, Inc. Upper Saddle River, New Jersey All rights reserved.

18 Principales características comerciales
Corriente máxima en directa, IFmax o IFM (DC forward current): Es la corriente continua máxima que puede atravesar el diodo en directa sin que este sufra ningún daño. Tres límites: Corriente máxima continua (IFM). Corriente de pico transitoria (Peak forward surge current), en la que se especifica también el tiempo que dura el pico. Corriente de pico repetitivo (Recurrent peak forward current), en la que se especifica la frecuencia máxima del pico. 2. Tensión de ruptura en polarización inversa (Breakdown Voltage, BV; Peak Inverse Voltage, PIV): Es la tensión a la que se produce el fenómeno de ruptura por avalancha. 3. Tensión máxima de trabajo en inversa (Maximun Working Inverse Voltage): Es la tensión que el fabricante recomienda no sobrepasar para una operación en inversa segura. 4. Corriente en inversa, IR (Reverse current): Es habitual que se exprese para diferentes valores de la tensión inversa 5. Caída de tensión en PD, VF (Forward Voltage): A veces no es 0.7 Volts.

19 Practical Applications of Diode Circuits
Slide 30 Practical Applications of Diode Circuits Rectifier Circuits Conversions of AC to DC for DC operated circuits Battery Charging Circuits Simple Diode Circuits Protective Circuits against Overcurrent Polarity Reversal Currents caused by an inductive kick in a relay circuit Zener Circuits Overvoltage Protection Setting Reference Voltages Robert Boylestad Digital Electronics Copyright ©2002 by Pearson Education, Inc. Upper Saddle River, New Jersey All rights reserved.