Chapter 19

2. Chapter 19 Integrated Circuits

3. Objectives • Define integrated circuit (IC). • Give a brief history of the IC. • Discuss the construction of an IC. • Illustrate the steps in construction of an IC. • Explain the operation of the operational amplifier. • Explain the operation of the 555 timer. Permission granted to reproduce for educational use only.

4. Integrated Circuits (ICs) • Also called chips • Include transistors, diodes, resistors, and capacitors Permission granted to reproduce for educational use only.

5. Transistors • Developed in 1947 • Served same purpose as triode amplifier • Did not require heat to operate • Solid-state and small • Used in small appliances • Used in early computers • Could quickly switch circuits Permission granted to reproduce for educational use only.

6. History of the IC • Developed in 1957 as a planar transistor on a silicon wafer • Micromodules made by printing components on a ceramic wafer • First commercially produced IC • Wiring connections caused problems • Silicon dioxide dopants protected and insulated PN junctions Permission granted to reproduce for educational use only.

7. Review What is an IC? A complete electronic circuit contained in one package, including transistors, diodes, resistors, and capacitors Permission granted to reproduce for educational use only.

8. Review What did Robert Noyce use to protect and insulate PN junctions? Silicon dioxide dopants Permission granted to reproduce for educational use only.

9. IC Construction • Circuit designer begins production • Layout designer creates technical drawing • Circuit layouts are photographically reduced • Photomasks are made from reduced layouts (Motorola) Permission granted to reproduce for educational use only.

10. Silicon Wafers • A seed is dipped into melted silicon • Silicon is sliced into wafers, with impurities added • Circuit is then built by layers on substrate • First layer is N-type, epitaxial layer Permission granted to reproduce for educational use only.

11. Silicon Dioxide Layer • Silicon dioxide is grown over the N-type material Permission granted to reproduce for educational use only.

12. Photoengraving Process • An emulsion of photoresist is added by photoengraving Permission granted to reproduce for educational use only.

13. Etching • Photoresist hardens where exposed • N-type silicon is left exposed • Hot gases and chemicals etch away N-type silicon Permission granted to reproduce for educational use only.

14. Diffusion • Continues to isolate parts of the IC from each other • Boron is used to diffuse the wafer • New layer of silicon dioxide forms over diffused P-type areas Permission granted to reproduce for educational use only.

15. Windows • Open windows are etched into the N layer and P-type regions • Wafer is given an oxide coating • Aluminum interconnections are added Permission granted to reproduce for educational use only.

16. Aluminum Interconnections • Form patterns between transistors, diodes, and resistors • Completed circuits are tested • Wafers are separated into individual chips (Motorola) Permission granted to reproduce for educational use only.

17. Resistors • Process used to make semiconductors is also used to make resistors, capacitors, and diodes Permission granted to reproduce for educational use only.

18. Capacitors Permission granted to reproduce for educational use only.

19. Circuit Integration Permission granted to reproduce for educational use only.

20. Linear ICs Analog devices or circuits Linear amplifiers Operational amplifiers (op amps) Voltage regulators or buffers Voltage comparators Analog switches Audio amplifier circuits Digital ICs Switches On or off positions Logic and gate circuits Common Types of ICs Permission granted to reproduce for educational use only.

21. Review What are the working plates made from the reduced layouts called? Photomasks Permission granted to reproduce for educational use only.

22. Review What is the first, or bottom, layer of the IC wafer made from? P-type silicon substrate Permission granted to reproduce for educational use only.

23. Review What is the light-sensitive emulsion that is placed over the N-type layer? Photoresist Permission granted to reproduce for educational use only.

24. Review How are the parts of the IC isolated from each other as they are constructed? Diffusion Permission granted to reproduce for educational use only.

25. Review What other components can be made using the method used to make semiconductor materials? Resistors, capacitors, and diodes Permission granted to reproduce for educational use only.

26. The 741 Op Amp • General purpose amplifier • High input impedance and low output impedance • Wide frequency response • Slight output voltage • Uses include power-supply regulator, signal generator, oscillator, timer, filter, and instrumentation Permission granted to reproduce for educational use only.

27. Op Amps • Single chip containing several transistors and resistors • No pin identification markings on the chip • Pins can be identified with specifications sheets and a reference point Permission granted to reproduce for educational use only.

28. Op Amps (Cont.) • Power is provided through two pins • One pin is connected to positive voltage of power supply • The other is connected to ground or the negative voltage • Offset null Permission granted to reproduce for educational use only.

29. Op Amp Gain • Determined by relationship of feedback resistor and input resistor • AV (inverting) = RF÷ RI • AV (noninverting) = (RF ÷ RI) + 1 Permission granted to reproduce for educational use only.

30. Comparator Circuits • Mode of operation • Output of comparator is driven to maximum positive or negative • Op amp will continue to put out an inverted signal until the inputs have a matching voltage amplitude Permission granted to reproduce for educational use only.

31. Review How can pins in an op amp be identified? With specifications sheets and a reference point Permission granted to reproduce for educational use only.

32. Review What is the calibration feature of an op amp called? Offset null Permission granted to reproduce for educational use only.

33. Review How is op amp gain determined? By the relationship of the feedback resistor and the input resistor Permission granted to reproduce for educational use only.

34. Review What is a comparator circuit? Op amp with inverting and noninverting inputs, in which the two inputs are compared to each other Permission granted to reproduce for educational use only.

35. 555 Timer • Very accurate timing device • Used for clocks, time delay circuits, sequential operation, and pulsing circuits • Monostable mode • Astable mode Permission granted to reproduce for educational use only.

36. Review What is the 555 timer used for? Highly accurate timing circuits with a range from a few microseconds to hours Permission granted to reproduce for educational use only.

37. Review What is the function of the astable mode? The timer puts out a repetitive signal from the output pin Permission granted to reproduce for educational use only.

38. For Discussion • Explain two primary functions of an electronic amplifier device. • How are resistors made on an IC chip? • What has caused the drop in IC cost in the past 10 years? Permission granted to reproduce for educational use only.