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Archive for the ‘Integrated Circuits’ Category

4000 Series IC’s

April 5, 2011 Leave a comment

The 4000 series is a large group of industry standard integrated circuits.  In the past they were known not to operate at as fast speeds as other popular chips at the time however they did use a lot less power consumption, and they had the ability to work over a larger range of voltages as well as having a simpler circuit design.  Their slower speed did limit them to static or slow speed designs but the series was extended in the late 1970s and 1980s to include new types of chip which implemented new or more greatly integrated functions or were better versions of existing chips in the series. Most of these newer chips were given 45xx and 45xxx designations, but are usually still regarded by engineers as part of the 4000 series. 

 The 4000 series IC have been used in space satellites for numerous decades and even into the new millenium  people building satellites still use 4000 series integrated circuits in their manufacture so they still have a major part to play in digital circuitry.  The series itself is huge and so for future reference I have found this usefel website that lists a few of the more popular 4000 series chips as well as some of their general characteristics.  It is also a useful aid to advise me on what sort of circuits I can create across this module to show competence.

 http://www.kpsec.freeuk.com/components/cmos.htm

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Categories: Integrated Circuits

Digital Integrated Circuits

March 20, 2011 Leave a comment

Integrated circuits are commonly grouped into two different types:   Analog/linear and digital/logic.  The more sophisticated integrated circuits will combine digital and analog functions to form a chip.  For example a digital chip may feature an analog/linear voltage regulator, while some analog chips may include a built in digital counter.  By combining integrated circuits it is possible to improve a products performance, or to give it a new feature such as adding a time delay to a counter which is usually only possible with the use of timers.

The chips themselves can come in many different packages. Common chips used at the moment would be the different varieties of DIP ( dual in- line package) chips.  Plastics and ceramics are the usual components of standard DIPs, although metals are also used, it is usually the case that manufacturers will replace the metal parts with the cheaper alternative plastic DIPS.  These chips usually have between 4 and 100 pins.

Digital IC’s are composed of gates with these gates functioning like switches which turn on and off.  A digital IC contains several gates and an integrated circuit that has two input gates is usually known as a logic gate.

If I increase the inputs and gates it can also increase the ability of the IC to perform logical operations.  Because of this digital IC’s are often used in information transfers and exchanges.  The integrated circuit itself is just a tiny component of common devices like computers but these devices rely on the efficency of the integrated circuits to function correctly.

Categories: Integrated Circuits

Integrated Circuits

March 18, 2011 Leave a comment

Integrated circuits enable us to not have to construct circuits with lots of individual discrete components such as transistors, diodes and resistors.  With an integrated circuit it is possible to fabricate a large number of the equivalent discrete components onto a tiny piece of silicon.  The resulting equivalent arrangement is far more compact than if all the components were separate and it is also considerably cheaper and much more reliable.  In books it is suggested that it is not necessary to have a detailed understanding of the internal circuitry of an IC in order to make effective use of it.  Instead I have to be aware of some basic rules concerning the supply voltage rails and input and output requirements.  A measure of the number of individual semiconductor devices within the chip is given by referring to its ‘scale of integration’ with the following terminology usually applied:

Scale of integration Abbreviation Number of logic gates or circuitry of equivalent complexity
Small SSI 1-10
Medium MSI 10-100
Large LSI 100-1000
Very large VLSI 1000-10000
Super large SLSI 10000-100000

 With the exception of only a few circuits, the availability of low cost integrated circuits has made discrete circuitry obsolete.  Integrated circuits hold a number of advantages of a discrete component circuit that is designed to fulfill the same job.

  •  They have a higher reliability despite their complexity
  •  They cost less than the equivalent discrete circuitry
  •  They have a much smaller space requirement, typically about 10% in comparison to discrete component circuit.
  •  They have an easier circuit layout.  Because they are designed to use a minimal number of external connections the layout is simplified.
  •  They have a matched performance.  The semi-conductor devices fabricated using IC technology usually have closely matched characteristics and tend to have a more assured performance than there would be with the number of variations in discrete component characteristics.

 The disadvantages of using an IC could be that they lack flexibility as it is not generally possible to modify the parameters within which an integrated circuit will operate as easily as it is to modify the performance of discrete circuitry.

 They may also have performance limitations where high currents, voltages, power levels, frequency signals and very low level signals are involved.

 IC’s are divided into two general classes which are linear (analogue) or digital.  Digital integrated circuits are comprised of logic gates.

Categories: Integrated Circuits

555 Timer

March 14, 2011 Leave a comment

The 555 timer is one of the most versatile IC’s ever produced.  It is a mixture of analogue and circuitry and its applications are virtually limitless in the world of digital pulse generation.  It can be used for producing accurate time delays or oscillation.  It can be used for applications such as precision timing, pulse generation, sequential timing, time delay generation and pulse width modulation (PWM)

The eight pins carry out the following functions:

  1. Ground, which acts as a safety measure as with electrical plugs
  2. Trigger, which passes on voltage to start the timing operations
  3. Output, which carries voltage to the device using the timer
  4. Reset, which is used to end the timing operation
  5. Control voltage, an optional pin used for controlling the timer from outside the main circuit set-up
  6. Threshold, which determines how long the timer should output voltage in each on/off cycle – in other words, how long the timing interval should be
  7. Discharge, connected to a capacitor which also influences the timing interval
  8. V+, which is the voltage input

There are three different types of use for a 555 timer.  The monostable operation as discussed in the ‘What is a digital circuit category’  is when the output signal simply switches between the default off position and a temporary on position at regular intervals, this is most commonly used for timers.

Astable operation is when the output voltage rises and falls in a set pattern, making it an oscillator. As the pattern can be varied, it can be used for any purpose which requires a particular tone pattern.

Bistable operation is when the signal can be held in one of two positions, meaning the 555 timer can act as the smallest possible unit of computer memory.

All IC timers require an outside capacitor to determine the on off times of the output pulses, it takes a period of time for a capacitor to charge or discharge through a resistor and theses times can be alternated by calculating the values of resistance and capacitance the time is easily worked out through this equation

T=RxC

So if I was to assume that a resistor had a value of 1 mega ohm and the capacitor a value of 1uF (microfarad) then the calculation would be

time =1,000,000 x 0.000001 and so for instance the time would be one second.

Categories: Integrated Circuits