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Let us understand what is an
Integrated Circuit or IC? This is very common term used in the field of
electronics. As the name clearly indicates it contains a complete circuit
integrated into it. It’s a semiconductor component. It can have tens or hundreds
or thousands even millions of transistors, resistors, diodes, small capacitors
and MOSFETs etc. bundled into it in a form of specific circuit and the usable input
and output pins are given externally to connect to other circuits or to mount
of PCB (Printed Circuit Board). These external pins are used to provide power
supply to IC, give required input signal, take output from it and connect few
external components to get different functions from it. All these hundreds and
thousands of components in it is manufactured on a small silicon die in square
or rectangular shape and size starting from around 1-2 mm and may go up to few
millimetres only. They come in different size depending on the function they
can perform and number of pins required to be given for external use in
circuits. Shape is mostly rectangular or square. As we can see in the image, we
have different size available with different number of pins.
Package:
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There are mostly two types of IC packages available for general use,
one is DIP and other is SIP. “Dual in line Package” and “Single
in line Package”. There are other types also but at this level we shall limit to basic types which can be used at beginning.
As we can see in picture, Dual in line package is simply having two
rows of external pins, each side having equal number of pins. Single in line package
is having only one row of external pins.
In both type of packages, we have a standard method to count the pin
number as shown here.
In DIP we can see either a
semicircle cut on one side or a “Dot” near one particular corner of the square
or rectangular package. Either one indication could be present or both. We need
to keep them on top side as shown in image. In this position pin-1 starts from
top left and gradually we have count the pins downward. Next when we reach the
other side of package, the next count starts from right bottom and ends at
right top (follow the way arrow shown in diagram).
For SIP there is there is again a “Dot” on one side and/or one side
top will be slanted as shown in image. Keep any of these available signs in
left and start counting from left as pin-1 and go straight to the right end.
Each pin in an IC is having different functions and should be
connected correctly else it will easily burn out. Where ever IC is used in any
circuit, the pin numbers are clearly specified in it and we should follow them
to connect correctly.
Some of the ICs used for high power application, also need metal heat
sink to dissipate excess heat generated, to avoid burnout. In such cases
appropriate size of heat sink should be used as suggested in particular
circuit.
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If we zoom in this image, we can see a square shining part in middle
which is nothing but actual chip made on a silicon base. That is too small and
is difficult to handle by normal user and is very sensitive also which can be
damaged easily. Hence to make it easy to handle and connect into circuit, the
outer black package is provided with metal pins which can be directly soldered
on board. If see carefully, you can see very fine wires going away from the
square shining chip visible from circular window. These are high quality fine
wires connecting the main chip with the external pins provided on both side of
outer package. This sample IC image is a very old obsolete 8-bit microcontroller IC which can be programmed to do specific task.
Every IC will have its number printed on it as we can see in all
images. So there is no coding is there to identify the number of an IC.
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As mentioned earlier that an IC contains a big number of individual
components packed densely into it. We can see a sample image of internal
circuit of an IC LM741. Image has been taken from data sheet of this IC. This
is very entry level IC which you can see contains around 20 nos. transistors
including P-N-P and N-P-N, 11 nos. resistors and 01 no. Capacitor, all in packed
in a small sized chip with dimension not more than 2mm. These numbers grow up
to some millions in our computer or mobile processor ICs. All the components
inside an IC are made up of Silicon base material.
In a circuit the IC can be shown as square/rectangular box or circle
or in triangle shape with IC number inside it and outer pins labeled with
respective pin numbers. Pins are shown in random places based on ease of
showing connection of other connected components.
Invention of IC is a boon in electronic industry because it helped in
reducing the size of electronic equipment. Else if you go back in history
before 1960, bulky Vacuum Tubes were used as diode and transistor. They were
bulky in size (height of few inches) and took time for the filament inside it
to heat up then your device will start working. In mid-1960 these vacuum tubes
started getting replaced with semiconductor transistors. Later when technology
improved we discovered ways to manufacture all basic components with Silicon in
miniature size, then we started making ICs. And as the technology is improving
further we are able to make more and more components in smaller area and
devices and gadgets are becoming smaller and smaller. In 2017 IBM created chip with 5 nm (Nano Meter) silicon chip which measured 50mm2 and had
600 million transistors per millimetre square. Samsung has announced to start mass
production of 5 nm chip from this quarter. So, you can imagine the density of
components inside a chip/IC which are being manufactured now a day.
That’s all about Integrated Circuits/Chips. Keep visiting for more
topics.
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