ElectronicsElectronics

Principles & ApplicationsPrinciples & ApplicationsFifth EditionFifth Edition

Chapter 13Integrated Circuits

©1999 Glencoe/McGraw-Hill

Charles A. Schuler

• IC fabrication• The 555 Timer• Additional ICs• Digital Signal Processing• Troubleshooting

INTRODUCTION

The base process is called photolithography.

• Silicon wafer (the substrate) oxidized on its surface

• Coated with photoresist

• Covered with a photomask

• Exposed to light and developed

• Etched to expose the substrate

• Impurity diffusion into the substrate

• Repeat five or more times

Silicon substrate

Start with a silicon substrateCoat with silicon dioxideCoat with photoresistCover with photomaskExpose with lightDevelopEtchDiffusion

Dopant

A PN junction has formed

Batch processing

Each wafer will yield dozens of ICs (or more).

Probetest

During the probe test, the defective ICs are marked.

After the wafer is scribed and separated,the defective ICs are discarded.

Using photolithography to form an NPN BJT

1. P-type substrate

2. N+ diffusion layer

3. N epitaxial layer

4. Silicon dioxide layer

5. Expose and etch

6. Boron diffusion

7. Silicon dioxide layer

8. Expose and etch

9. Boron base diffusion

10. Emitter diffusion

Using photolithography to form an NPN BJT

11. Coat, expose and etch

12. Aluminum metalization layer

13. Coat, expose and etch away extra aluminum

Collector contact Emitter contact

Base contact

IC fabrication quiz

The base process in making monolithic ICsis _______________. photolithography

The wafer is coated with photoresist andexposed through a _________. photomask

Etching produces windows through whichimpurities are ________. diffused

The electrical performance of each chip on thewafer is checked during the ____ test. probe

Individual sections are electrically connectedwith a film of __________. aluminum

5 k

R

S Q

Q5 k

5 k

Gnd1

Out

3

+VCC8Discharge

Threshold

Control

Trigger

7

6

5

2

555555

Reset4

UTP VCC

LTP VCC

A popular timer IC

SRQ

Q

R

S Q

Q

How the RS flip-flop in the 555 timer works:

Once set, the Q output remainshigh until the flip-flop is reset.

Outputs are inopposite states.

1

3

+VCC

7

6

2

8One-shot operation

R

C

VCC

The input trigger resets the flip-flop and C then chargesuntil the top comparator trips and sets the flip-flop.

SR

input triggeroutput pulse

Dischargetransistor

+ VCC

555

48

7

6

1

3

2

R

C

t = 1.1RCOutput pulse

Trigger1/3 VCC

The external components determine the output pulse width.

1

3

+VCC

7

6

2

8

Free-running orastable operationRB

C

RA

SR

VCC

VCC

C charges through RA+ RB

and discharges through RB.

+ VCC

555

48

7

6

1

3

2

RA

C

Astablemode duty

cycle > 50%

RB

f =1.45

(RA + 2RB)C

Duty Cycle = RA + 2RB

x 100%RA + RB

+ VCC

555

48

7

6

1

3

2

RA

C

Astablemode duty

cycle < 50%

RB

f =1.45

(RA + RB)C

RADuty Cycle =

RA + RB

x 100%

C chargesthrough RA

and dischargesthrough RB.

+ VCC

555

48

6

1

3

2

R

C

Trigger

Time-delaymode

Time delay = 1.1 RCOutput

555 timer quiz

The voltage of the trigger signal must beless than _________. VCC

The threshold and trigger comparatorscontrol the ___________. RS flip-flop

The Q output of the RS flip-flop controlsthe __________ transistor. discharge

In one-shot mode, the external R and C setthe _______ of the output pulse. width

In astable mode, the 555 timer acts as an____________. oscillator

ErrorAmplifier

Phasedetector

LPF

VCO

Phase-locked loop

In

In

VCO

The VCO locks onto the input phase.

ErrorAmplifier

Phasedetector

LPF

VCO

In

The VCO also locks onto the input frequency.

Out

Ou

tpu

t vo

ltag

e

Input frequency

Lock range

ErrorAmplifier

Phasedetector

LPF

VCO

In

PLLs can serve as FM detectors.

Out

ErrorAmplifier

Phasedetector

LPF

VCO

fREF

PLL frequency synthesizer

fOUT

Digitaldivide by N fOUT = N(fREF)

DSP can replace several types of analog circuits

• Filters

• Noise reduction circuits

• Interference reduction circuits

• Compressors and expanders

• Modulators and demodulators

• Special effects circuits

• Echo canceling circuits

MemoryA/Dconverter

Sample& hold

LPFD/Aconverter

Processor

Digital signal processing

01101110110010001100001001101110000011100000100101101110

In

MemoryA/Dconverter

Sample& hold

LPFD/Aconverter

Processor

Digital signal processing

01101110110010001100001001101110000011100000100101101110

In

01100010110010111100001001101011000011100001100101101111

Out

4-bit D/A converter

Vout

R R

2R

4R

8R

Output states = 2N = 24 = 16

N = 4

5 V8

5 V0 V

-9.375 V

Troubleshooting

• Be sure to take a system point-of-view

• Supply voltages may be critical

• Waveform analysis is often used

• Sampling/clock rate in DSP is important

• The software and/or coefficients are critical in DSP systems

• Check A/D and D/A converters

IC applications quiz

When a PLL is locked, the VCO tracks theinput _________. signal

PLLs can be used as FM _________.detectors

With a divide by N, a PLL serves as afrequency _____________. synthesizer

In DSP systems, analog signals are firstconverted to _______ signals. digital

The output of a 6-bit D/A converter has_______ possible output levels. 64

REVIEW

• Fabrication• The 555 Timer• Additional ICs• Digital Signal Processing• Troubleshooting