Neamen Microelectronics, 4eChapter 2-1 McGraw-Hill Microelectronics Circuit Analysis and Design...

Neamen Microelectronics, 4e Chapter 2-1 McGraw-Hill

Microelectronics Circuit Analysis and Design

Donald A. Neamen

Chapter 2

Diode Circuits

Neamen Microelectronics, 4e Chapter 2-2 McGraw-Hill

In this chapter, we will:

Determine the operation and characteristics of diode rectifier circuits, which is the first stage of the process of converting an ac signal into a dc signal in the electronic power supply.

Apply the characteristics of the Zener diode to a Zener diode voltage regulator circuit.

Apply the nonlinear characteristics of diodes to create waveshaping circuits known as clippers and clampers.

Examine the techniques used to analyze circuits that contain more than one diode.

Understand the operation and characteristics of specialized photodiode and light-emitting diode circuits.

Neamen Microelectronics, 4e Chapter 2-3 McGraw-Hill

Block Diagram for ac to dc Converter

The diode rectifier, filter, and voltage regulator are diode circuits.

Neamen Microelectronics, 4e Chapter 2-4 McGraw-Hill

Problem-Solving Technique: Diode Circuits

1. Determine the input voltage condition such that the diode is conducting (on).a. Find the output signal for this condition.

2. Determine the input voltage such that the diode is not conducting (off).a. Find the output signal for this condition.

Neamen Microelectronics, 4e Chapter 2-5 McGraw-Hill

Half-Wave Rectifier

Voltage Transfer Characteristics

Neamen Microelectronics, 4e Chapter 2-6 McGraw-Hill

Signals of Half Wave Rectifier

Input voltage Output voltage

Diode voltage

Neamen Microelectronics, 4e Chapter 2-7 McGraw-Hill

Load Line Analysis

Load line when vS is at its maximum forward voltage.

Load line when vS is at its most negative value.

Neamen Microelectronics, 4e Chapter 2-8 McGraw-Hill

Load Line (con’t)

As vS varies with time, the load line also changes, which changes the Q-point (vD and iD) of the diode.

Neamen Microelectronics, 4e Chapter 2-9 McGraw-Hill

Half-Wave Rectifier as Battery Charger

Neamen Microelectronics, 4e Chapter 2-10

McGraw-Hill

Full-Wave Rectifier

Voltage transfer characteristics

Input and output waveforms

Neamen Microelectronics, 4e Chapter 2-11

McGraw-Hill

Full-Wave Bridge Rectifier

When vS is positive, D1 and D2 are turned on (a). When vS is negative, D3 and D4 are turned on (b).

In either case, current flows through R in the same direction, resulting in an output voltage, vO, shown in (c).

Neamen Microelectronics, 4e Chapter 2-12

McGraw-Hill

Full-Wave Bridge Rectifier

Neamen Microelectronics, 4e Chapter 2-13

McGraw-Hill

Output Voltage of Full-Wave Rectifier with RC Filter

The ripple on the ‘dc’ output isP

Mr T

ffRC

VV

2

1 where

2

Neamen Microelectronics, 4e Chapter 2-14

McGraw-Hill

Output Voltage of Full-Wave Rectifier with RC Filter

Diode conducts current for only a small portion of the period.

M

r

V

V

T

t 21

Neamen Microelectronics, 4e Chapter 2-15

McGraw-Hill

Equivalent Circuit During Capacitance Charging Cycle

M

r

MpeakC

MC

V

Vt

tCVi

tCVi

2

,

Neamen Microelectronics, 4e Chapter 2-16

McGraw-Hill

PSpice Schematic of Diode Bridge Circuit

Steady state output voltage for a 60Hz sine wave input with peak value of 13.4V.

Neamen Microelectronics, 4e Chapter 2-17

McGraw-Hill

Demodulation of Amplitude-Modulated Signal

Modulated input signal

Detector circuit

Demodulated output signal

Neamen Microelectronics, 4e Chapter 2-18

McGraw-Hill

Voltage Doubler Circuit

Neamen Microelectronics, 4e Chapter 2-19

McGraw-Hill

Equivalent Circuits for Input Cycles

Negative input cycle Positive input cycle

Neamen Microelectronics, 4e Chapter 2-20

McGraw-Hill

Voltage Regulator

The characteristics of the Zener diode determines VL.

LIZ

i

ZPSI

L

ZL

III

R

VVI

R

VI

Neamen Microelectronics, 4e Chapter 2-21

McGraw-Hill

Design Example 2.5

Neamen Microelectronics, 4e Chapter 2-22

McGraw-Hill

Load Line Analysis

The reverse bias I-V is important for Zener diodes.

Neamen Microelectronics, 4e Chapter 2-23

McGraw-Hill

The Zener diode begins to conduct when VPS = VZ.

When VPS ≥ VZ: VL = VZ

IL = VZ/RL,, but VZ ≠ constant

I1 = (VPS – VZ)/Ri

IZ = I1 - IL

Voltage Rectifier with nonzero Zener resistance

Neamen Microelectronics, 4e Chapter 2-24

McGraw-Hill

Voltage Transfer Characteristics of Limiter Circuit

Neamen Microelectronics, 4e Chapter 2-25

McGraw-Hill

Single Diode Clipper

Neamen Microelectronics, 4e Chapter 2-26

McGraw-Hill

Additional Diode

Clipper Circuits

Neamen Microelectronics, 4e Chapter 2-27

McGraw-Hill

Parallel-Based Diode Clipper Circuit

Neamen Microelectronics, 4e Chapter 2-28

McGraw-Hill

Series-Based Diode Clipper

Circuits

Neamen Microelectronics, 4e Chapter 2-29

McGraw-Hill

Parallel-Based Clipper Circuit Using Zener Diodes

Neamen Microelectronics, 4e Chapter 2-30

McGraw-Hill

Diode Clamper Circuit

Neamen Microelectronics, 4e Chapter 2-31

McGraw-Hill

Diode Clamper Circuit with Voltage Source

Neamen Microelectronics, 4e Chapter 2-32

McGraw-Hill

Diode and Resistor In Series

Voltage shift between input and output voltages in transfer characteristics is because the diode only conducts when v1 ≥ V.

Neamen Microelectronics, 4e Chapter 2-33

McGraw-Hill

Diode with Input Voltage Source

Output voltage is a constant when the diode is not conducting, when v1 ≥ Vs - V.

Neamen Microelectronics, 4e Chapter 2-34

McGraw-Hill

2 Diode Circuit

Voltage transfer characteristics

Neamen Microelectronics, 4e Chapter 2-35

McGraw-Hill

Problem-Solving Technique: Multiple Diode Circuits

1. Assume the state of the diode. a. If assumed on, VD = V

b. If assumed off, ID = 0.

2. Analyze the ‘linear’ circuit with assumed diode states.

3. Evaluate the resulting state of each diode.4. If any initial assumptions are proven

incorrect, make new assumption and return to Step 2.

Neamen Microelectronics, 4e Chapter 2-36

McGraw-Hill

Exercise problem

D1 is not on.

D2 is on. This pins VO to -0.6V

Neamen Microelectronics, 4e Chapter 2-37

McGraw-Hill

Diode Logic Circuits:2-Input OR Gate

V1 (V) V2 (V) VO (V)

0 0 0

5 0 4.3

0 5 4.3

5 5 4.3

V = 0.7V

Neamen Microelectronics, 4e Chapter 2-38

McGraw-Hill

Diode Logic Circuits:2-Input AND Gate

V1 (V)

V2

(V)VO

(V)

0 0 0

5 0 0

0 5 0

5 5 4.3

V = 0.7V

Neamen Microelectronics, 4e Chapter 2-39

McGraw-Hill

Photodiode Circuit

Neamen Microelectronics, 4e Chapter 2-40

McGraw-Hill

Optoisolator

Neamen Microelectronics, 4e Chapter 2-41

McGraw-Hill

Design DC Power Supply Circuit