Active Components & Integrated Circuits Chapter Four Active Components & Integrated Circuits

Introduction Basic solid-state electronic devices are described, and some idea of the powerful uses of digital electronics is given.

Active Electrical Components Background Passive vs. Active electrical components. Active: require an external source of power in order to work. Vacuum Tubes are an example of the early types of active components. Many electronic functions were possible using tubes, but there were serious limitations, these are:

Vacuum tubes Tubes require high voltages to operate (250 – 300V). They dissipate large amounts of heat. They wear themselves out and need to be periodically replaced. They were expensive to produce and fragile. Tubes still find their way in certain applications (microtubes in the military).

Transistors These replaced vacuum tubes in many applications, because: They are small in size. They require little power to operate. They are mechanically very rugged. They are operated on low voltages (12V or less). They are extremely simple in structure.

What is a transistor? A piece of semiconductor material chemically treated to have some desired electrical properties. Semiconducting materials conduct electricity better than insulators but much poorer than conductors. Typically it has three terminals (BJT: Emitter, Base, Collector; MOS: Drain, Gate, Source). Current amplifier: allows small (base) current to control much larger current (collector).

What is a transistor? Can be used as ON/OFF Switch (Electronic switch) In order to operate the transistor it should be connected in a circuit with the proper components MOS transistor Bipolar junction transistor

Integrated Circuits Transistors and their associated circuits are manufactured on the same piece of semiconductor material (chip or IC) Microprocessors contain millions of transistors are fabricated on a single chip due to the development in IC technology. ICs are used in both digital and analog applications, there are thousands of different chips in the market. The operating parameters & schematic diagrams are provided in Data books put out by the manufacturing companies (TTL, Synertek, Intel, Motorola).

Digital Electronics Electronics can be divided into two areas: Digital: based on the binary number system and the output can assume only two values (ON=1=+5V DC, OFF=0=0V DC). Analog (amplifier output might be any voltage from say -5V to +5V). Digital electronics is the basis of operation of computers.

The Binary Number System Numbers are represented in computers using the binary number system. The reason for using the binary system is that the transistors internal to the computer chip act as simple switches. The decimal system can be converted to the binary system so the binary system does not limit the capability of a computer to make calculations.

Logic Families Families differ in: the way the transistors are connected together, switching speeds, power consumption, operating voltage levels, and other electrical characteristics. TTL: Transistor-Transistor Logic CMOS: Complementary Metal Oxide Semiconductor ECL: Emitter Coupled Logic Applications determine which family to use.

Simple logic functions Inverter. Symbol Truth table B A B A 1

Simple logic functions AND Gate Symbol Truth table C B A 1

Simple logic functions OR Gate Symbol Truth table C B A 1

Example 15 cents toll. Only nickels (5 cents) and dimes (10 cents) can be deposited. N= number of nickels deposited D= number of dimes deposited G= command to raise gate G=0 if 15 cents is not deposited G=1 if 15 cents is deposited

Circuit Implementation G=n1n2+n1d1, n1=1Nickel, n2=2Nickels,d=1 Dime

The truth table g d1 n2 n1 1