Electronics Principles & Applications Fifth Edition Chapter 13 Integrated 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 dioxide Coat with photoresist Cover with photomask Expose with light Develop Etch Diffusion Dopant A PN junction has formed

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

Probe test

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 ICs is _______________. photolithography The wafer is coated with photoresist and exposed through a _________. photomask Etching produces windows through which impurities are ________. diffused The electrical performance of each chip on the wafer is checked during the ____ test. probe Individual sections are electrically connected with a film of __________. aluminum

5 k  R SQ Q Gnd1 Out 3 +V CC 8 Discharge Threshold Control Trigger Reset4 UTP  V CC LTP  V CC A popular timer IC

S R Q Q R SQ Q How the RS flip-flop in the 555 timer works: Once set, the Q output remains high until the flip-flop is reset. Outputs are in opposite states.

1 3 +V CC One-shot operation R C  V CC The input trigger resets the flip-flop and C then charges until the top comparator trips and sets the flip-flop. S R input trigger output pulse Discharge transistor

+ V CC R C t = 1.1RC Output pulse Trigger 1/3 V CC The external components determine the output pulse width.

1 3 +V CC Free-running or astable operation RBRB C RARA S R  V CC  V CC C charges through R A + R B and discharges through R B.

+ V CC RARA C Astable mode duty cycle > 50% RBRB f = 1.45 (R A + 2R B )C Duty Cycle = R A + 2R B x 100% R A + R B

+ V CC RARA C Astable mode duty cycle < 50% RBRB f = 1.45 (R A + R B )C RARA Duty Cycle = R A + R B x 100% C charges through R A and discharges through R B.

+ V CC R C Trigger Time-delay mode Time delay = 1.1 RC Output

555 timer quiz The voltage of the trigger signal must be less than  _________. V CC The threshold and trigger comparators control the ___________. RS flip-flop The Q output of the RS flip-flop controls the __________ transistor. discharge In one-shot mode, the external R and C set the _______ of the output pulse. width In astable mode, the 555 timer acts as an ____________. oscillator

Error Amplifier Phase detector LPF VCO Phase-locked loop In VCO The VCO locks onto the input phase.

Error Amplifier Phase detector LPF VCO In The VCO also locks onto the input frequency. Out Output voltage Input frequency Lock range

Error Amplifier Phase detector LPF VCO In PLLs can serve as FM detectors. Out

Error Amplifier Phase detector LPF VCO f REF PLL frequency synthesizer f OUT Digital divide by N f OUT = N(f REF )

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

Memory A/D converter Sample & hold LPF D/A converter Processor Digital signal processing In

Memory A/D converter Sample & hold LPF D/A converter Processor Digital signal processing In Out

4-bit D/A converter V out R R 2R 4R 8R Output states = 2 N = 2 4 = 16 N = 4 5 V 8 0 V 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 the input _________. signal PLLs can be used as FM _________. detectors With a divide by N, a PLL serves as a frequency _____________. synthesizer In DSP systems, analog signals are first converted 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