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IC packages and applications

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ICs are mounted in packages that protect them from moisture, dust and contaminants and the packaging makes it easier to install the ICs.

The most popular IC package is the dual in-line package (DIP), this package has two rows of mounting pins or leads.

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These packages are available to accommodate SSI, MSI and LSI circuitry and can be constructed of either plastic or ceramic materials.

Plastic packages are used in applications where operating ranges fall within 0 to 70 Centigrade, 32 to 158 F.

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Ceramic packages are more expensive but offer better protection against moisture and contaminants, their operating temperatures are -55 to 125 degrees centigrade.

Some ICs are a combination of several monolithic chips in one dual line package.

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A flat pack is another type of IC that is very thin and the leads extend horizontally.

ICs can also be mounted in metal cans and this allows for a variety of installation possibilities.

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Surface mount technology (SMT) has introduced four new IC packages:

1. SOIC – small outline IC2. PLCC –plastic leaded chip carrier3. LDCC – leaded ceramic chip carrier4. LCC – leadless chip carrier

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Integrated circuits fall under two general categories digital ICs or linear ICs and are used for various types of logic circuits.

Linear ICs provide an output signal that is proportional to the input signal and are used to provide amplification and regulation.

Linear ICs are used in TVs, radios, power supplies and communication equipment.

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Digital ICs are the most widely used and are designed for logic circuits found in computers.

Digital ICs use discrete values, either 0 or 1 to perform 3 general functions called logic gates:

1. AND2. OR 3. NOT

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These gates are combined to make decisions based on digital input information and are referred to as digital logic gates.

Logic gates let computers make very simple decisions using a mathematical technique called Boolean algebra.

Truth tables are used to show all of the possible inputs and outputs of the AND, OR and NOT logic gates.

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It is only possible to have an output of either a 1 or a 0 which are represented by voltages.

A voltage of approximately 3V or higher represent a logic of 1 and voltages of 0.7 and less represent a logic of 0.

The AND gate has an output of 1 only when all of it’s inputs are equal to 1, this is similar to a multiplier table, the only possibilities in a digital circuit are 0 X 1 = 0 and 1 X 1 = 1.

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Below is the AND truth table the AND logic symbol and a schematic representation of the symbol.

In the schematic, unless both switches close there is no output

A B X

0 0 0

0 1 0

1 0 0

1 1 1

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Below is the OR truth table, the OR logic symbol and the schematic representation of the OR symbol.

The OR table is an addition function, the output will equal 1 when any or all of the

inputs equal 1.A B X0 0 0

0 1 1

1 0 1

1 1 1

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Below is the NOT table, the NOT logic symbol and the schematic representation of the symbol.

The NOT gate always provides an output that is the opposite of the input, the NOT gate is commonly called the inverter.

IN OUT

O 1

1 0

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Below is a combination logic circuit that use 3 NOT gates, 2 AND gates and 1 OR gate with three outcomes; A is less than B, A is greater than B and A = B.

A B X1 X2 X3

0 0 0 0 1

0 1 1 0 0

1 0 0 1 0

1 1 0 0 1

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These combination logic circuits are sometimes referred to a choice boxes, the equivalent symbol is shown below.

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A NAND gate (Negated AND or NOT AND) is a logic gate which produces an output that is false only if all its inputs are true. A LOW (0) output results only if both the inputs to the gate are HIGH (1); if one or both inputs are LOW (0), a HIGH (1) output results. A B OUTPUT

0 0 1

0 1 1

1 0 1

1 1 0

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The NAND gate is significant because any boolean function can be implemented by using a combination of NAND gates, this property is called functional completeness.

In complicated logical expressions, normally written in terms of other logic functions such as AND, OR, and NOT, writing these in terms of NAND saves on cost because implementing such circuits using NAND gate yields a more compact result.

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As mentioned earlier, linear ICs are used for amplification, below is a diagram of a basic op amp.

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An operational amplifier (Op-Amp) is a differential amplifier that amplifies the difference of voltages applied to its two input terminals (differential input), and provides a single-ended output.

Op amps are sold as a complete package and can be used in a variety of applications.

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The op amp is actually three separate amplifier circuits in the same package; a differential amp, a voltage amp and an output amp.

Below is the symbol for an op amp with three or five leads