Introduction to Digital Logic Missouri S&T University CPE 2210 Electric Circuits

Transcription

1 Introduction to Digital Logic Missouri S&T University CPE 2210 Electric Circuits Egemen K. Çetinkaya Egemen K. Çetinkaya Department of Electrical & Computer Engineering Missouri University of Science and Technology 7 February 2018 rev Egemen K. Çetinkaya

2 Introduction Basics of electric circuits Transistors Summary Electric Circuits Outline 2

3 Digital Systems Components analog phenomena electric signal A2D digital data digital data sensors and other inputs Digital System D2A electric signal actuators and other outputs digital data digital data Transducer: sensor + actuator Not all sensors/actuators require A2D/D2A conversion Digital system can be implemented: microprocessor readily available, cheap, easy to program, easy to reprogram custom circuit smaller, faster, consume less power 3

4 Digital Logic Circuit Types What are the type of digital circuits? 4

5 Digital Logic Circuit Types What are the type of digital circuits? Combinatorial output solely depends on present values of input(s) no memory basic blocks of circuits e.g.: lamp with light sensor Sequential output depends on present and past values of input(s) output depends on present state e.g.: calculator 5

6 Combinatorial Logic Types Doorbell Example Egemen K. Çetinkaya b=0 Digital F=0 System b=1 Digital F=1 System if b=0, then F=0 if b=1, then F=1 Doorbell rings only when button is pressed output determined from input 6

7 Combinatorial Logic Types Sensor Example Motion sensor a Digital System F Lamp Light sensor b if a=0 and b=0, then F=0 if a=0 and b=1, then F=0 if a=1 and b=0, then F=1 if a=1 and b=1, then F=0 Lamp is on only when there is motion and it is dark output determined from input 7

8 Sequential Logic Types Toggle Lamp Example Egemen K. Çetinkaya b=0 Digital F=0 System b=1 Digital F=1 System b=0 Digital F=1 System Cannot determine value of F solely from present input value Output cannot be determined from input value output depends on past and present values in other words there is memory 8

9 Voltage: Electric Circuits Ohm s Law difference in electric potential between two points unit: volt (V), symbol: V Current: flow of charged particles unit: ampere (A), symbol: I Resistance: tendency of wire to resist the flow of current unit: ohm (Ω), symbol: R Ohm s law: V=IR 9

10 5 A Egemen K. Çetinkaya Ohm s Law Example 10 V + 5 A 2 ohms 0V 10 V 5 A What is the resistance of the light bulb? given 10 V battery and 5 A current flow 10

11 Electric Circuits Switch Evolution Switches are basis of all digital circuits Evolution 1930s: electromagnetic relays moving parts, slow 1940s: vacuum tubes no moving parts consumed a lot of power, generated a lot of heat 1950s: transistors (1956 Nobel Prize) faster, cheaper, reliable 1960s: integrated circuits (IC) multiple transistors on chip; billions in ~ 600 mm

12 Electric Circuits Scale of Transistor Integration in IC Egemen K. Çetinkaya Scale of transistor combination in Integrated Circuits Name Year Transistor number small-scale integration (SSI) medium-scale integration (MSI) large-scale integration (LSI) K very-large-scale integration (VLSI) K 1M ultra-large-scale integration (ULSI) M and more 12

13 Electric Circuits Switch Parts and States Switches have three parts source input output control input Switch has two states on off source input source input control input control input off output on output 13

14 Electric Circuits Switch Operation Example Switches operate like water faucet Question: lights on or off? Battery x = 0 Light Battery x = 1 Light 14

15 Electric Circuits Series Switch Operation Example Question: lights on or off? Egemen K. Çetinkaya Battery Light Battery Light 15

16 Electric Circuits Parallel Switch Operation Example Question: lights on or off? Egemen K. Çetinkaya Battery Light Battery Light 16

17 Electric Circuit Components Transistors Transistor: basic switching component in circuits other important use? BJT: Bipolar Junction Transistor MOSFET: Metal Oxide Semiconductor Field-Effect Transistor use of one : NMOS: N-type transistor PMOS: P-type transistor CMOS: Complementary Metal-Oxide-Semiconductor CMOS technology uses NMOS and PMOS together 17

18 Electric Circuit Components CMOS Transistor Operation Egemen K. Çetinkaya 18

19 Electric Circuit Components CMOS Transistor Operation A positive voltage here......attracts electrons here, turning the channel between the source and drain into a conductor Egemen K. Çetinkaya gate source oxide drain IC package (a) IC Silicon -- not quite a conductor or insulator: Semiconductor More on EE2200 class (Electronic Devices) 19

20 Electric Circuit Components Transistors NMOS transistor conducts when the gate is on Egemen K. Çetinkaya NMOS gate 1 0 conducts does not conduct 20

21 Electric Circuit Components Transistors PMOS transistor conducts when the gate is off Egemen K. Çetinkaya PMOS gate 1 0 does not conduct conducts 21

22 Transistor logic Examples 22

23 Electric Circuits Summary There are two types of digital circuits combinatorial circuits: no memory sequential circuits: memory Ohm s law: V=IR Switches are basic components of digital circuits Switches have two states: on and off Transistors are basic electric circuit component CMOS have NMOS and PMOS transistors together NMOS transistors conduct when gate is on PMOS transistors conduct when gate is off 23

24 References and Further Reading [V2011] Frank Vahid, Digital Design with RTL Design, VHDL, and Verilog, 2nd edition, Wiley, [BV2009] Stephen Brown and Zvonko Vranesic, Fundamentals of Digital Logic with VHDL Design, 3rd edition, McGraw-Hill, [S2017] John Seiffertt, Digital Logic for Computing, 1st edition, Springer,

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