Integrated Circuits, Digital & Linear ---------- --------- ------- - ------ An integrated circuit (IC) is a complete electronic circuit in one package. Usually this package includes transistprs, diodes, resistors, and capacitors with the connecting wiring and diodes. One major advantage of the integrated circuit is its size. It would be possible to wire all the individual or discrete components used in an IC, however, they would take up much more space. With the advantage of IC's it is possible to have high capacity computers that can literally fit in a suitcase. Integrated circuits are very reliable as compared to individual components. There is another advantage of lower cost. Integrated circuits can be classified into two basic types: 1. Digital 2. Linear Digital integrated circuits are used as switches and opperate in either on or off conditions. Linear integrated circuits are used as amplifiers and have variable outputs. Digital Integrated Circuits Digital integrated circuits handle digital information by using switching circuits. They work as a result of combining gating circuits and flip-flop circuits. Let us look at gates and how they operate by using binary logic. The Binary Numbering System Electronic circuits can be made to act in only two discrete states: On and Off. This two state system called Binary can be compared to a single-pole, single-throw (SPST) switch. In actual circuits, it is not very practical to build large electronic logic circuits using manual switches. They do, however, provide an easy basis for understanding other switchable electronic components. The most common electronic component that can be used as a switch is a transistor. These can allow current to flow through them which can be an On or 1 stage or they can be in cutoff condition representing the 0 in the binary numbering system. Simple circuits made up of diodes, transistors, and resistors can be used to perform the basic logic functions. Since the development of the integrated circuit (IC), tens or hundreds of circuits can be designed and fabricated into a single semiconductor chip. With only one SPST switch, you can only count up to a maximum of 1. Suppose you wanted to count higher, how can the binary system be used for a number such as 45 or 79? A basic concept governs the process of counting in any system. This concept is: You must record digit, one after each other, for each count until the count exceeds the total number of inputs available: Then you should start a second column and continue counting. The digit 0 in the decimal system is 0 in the binary system. Likewise the digit 1 in the decialm system is 1 in the binary system. However the number 3 in the decimal system is represented by the number 11 in the binary system. Logic Gates Electronic switching circuits that can be used with digital inputs are called Logic Gates. By using digital and linear circuits, decisions can be made. The circuits we will now discuss are the basic building blocks used in a large computer. They are important in helping the computer make the calculations and decisions it can do so well in extremely short periods of time. The basic types of logic gates are: 1. AND Gates 2. OR Gates 3. NOT Gates 4. NAND Gates 5. NOR Gates AND Gates Let us start with the AND gate to see how each of these logic gates operate. The AND gate is an electronic circuit that takes Yes and No inputs. It makes certain basic decisions with the output also expressed in Yes or No. As previously discussed, Yes or No data is binary in nature. This can indicate that there are two levels of current (or no current) in a circuit. Also Yes or No can be described as 1 or 0. The operation of an AND gate is best described as an electronic circuit that will produce an output of 1 (YES) if all of the inputs are 1 (YES). The AND gate is used to determine the presence of YES signals or 1's on both the inputs, A and B. When this occurs, the output signal will be 1. OR Gates The OR gate will provide an output signal of 1 (Yes) when either one or the other of its inputs is 1 (Yes). Likewise, if any of the inputs are 0 in an OR gate, the output is 0 (No). The OR circuit is normally used in electronic circuits to see if any input is present. NOT Gates The NOT gate is often referred to as an "inverter" because this is what it does in a circuit. The NOT gate is put into a circuit to invert the polarity of the input signal. If the input signal is 1 or Yes, the output signal will be 0 or No. Likewise if the input signal is 0, the output will be 1. NAND Gate All logic gates are combinations of the basic gates: AND, OR, and NOT. The NAND is a negative AND gate. It is made up of an AND gate and a NOT gate that inverts the output. Sometimes it is called a NOT-AND gate. NOR Gate The NOR gate is to the OR gate what the NAND gate was to the AND gate. It gives the opposite (or negative) results of the OR gate. It is made up of an OR gate and a NOT gate (inverter). The NOR circuit can be used if you want to see if there is any kind of input. If there is no input, the output will be 1. Conversely, if there is an input, there will be no (0) output. Linear Integrated Circuits Linear integrated circuits are the type that amplify signals or regulate them. They may be compared with digital ICs which may act as switches. The output of a linear integrated circuit is not abrupt as "on" or "off," however, it is smooth. The primary function of linear ICs is to amplify - to increase the gain of the circuit which means to increase the voltage, current or power. In any linear integrated circuit , output always remains proportional to the input level. This circuit is abbreviated LIC. Operational Amplifier One important type of linear integrated circuit is the Operational Amplifier, or "OP-AMP." An operational amplifier is a high gain linear integrated circuit that uses direct-coupling. You will find that operational amplifiers may be used in circuits such as audio and video amplifiers, power supplies, or as oscillators. Linear integrated circuits come in many shapes and sizes.