To Study the Equipments Used in the Semiconductor Lab

8/6/2019 To Study the Equipments Used in the Semiconductor Lab

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Semiconductor Devices

Lab Report

Submitted to:

Mam Maira

Submitted by:

Hafiz Waseeq Ahmed

Roll No. :

10 EL 88

Section:

A

Group:

B

Department Of Electrical Engineering

FAISALABAD


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To Study the Equipments used in the Semiconductor Lab

1.Oscilloscope2.Function Generator3.LCR Meter4.Dual Power Supply

1.Cathode Ray Oscilloscope:A cathode ray oscilloscope (C.R.O) is an instrument that converts

electronic and electrical signals to a visual display. The graph producedconsists of a horizontal axis which is normally a function of time, and avertical axis which is a function of the input voltage. The components ina cathode ray tube consist of a vacuum glass tube with an electron gun,a deflection system for deflecting the electron beam and a fluorescentcoated screen.

Description of different part:

The basic oscilloscope is typically divided into four sections: thedisplay, vertical controls, horizontal controls and trigger controls. Thedisplay is laid out with both horizontal and vertical reference lines

referred to as the graticule. In addition to the screen, most displaysections are equipped with three basic controls, a focus knob, anintensity knob and a beam finder button.The vertical section controls the amplitude of the displayed signal.This section carries a Volts-per-Division (Volts/Div) selector knob, anAC/DC/Ground selector switch and the vertical (primary) input for the


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instrument. Additionally, this section is typically equipped with thevertical beam position knob.The horizontal section controls the time base or sweep of theinstrument. The primary control is the Seconds-per-Division (Sec/Div)selector switch. Also included is a horizontal input for plotting dual X-Yaxis signals. The horizontal beam position knob is generally located inthis section.The trigger section controls the start event of the sweep. The triggercan be set to automatically restart after each sweep or it can beconfigured to respond to an internal or external event. An externaltrigger input (EXT Input) and level adjustment will also be included.

Focus control:

This control adjusts focus to obtain the sharpest, most-detailedtrace. In practice, focus needs to be adjusted slightly when observingquite-different signals, which means that it needs to be an externalcontrol. Flat-panel displays do not need a focus control, their sharpnessis always optimum.

Intensity control:This adjusts trace brightness. Slow traces on CRT oscilloscopes

need less, and fast ones, especially if not often repeated, require more.

Holdoff control:

Found on some better analog oscilloscopes, this varies the time(holdoff) during which the sweep circuit ignores triggers. It provides a

stable display of some repetitive events in which some triggers wouldcreate confusing displays. It is usually set to minimum, because a longertime decreases the number of sweeps per second, resulting in a dimmertrace.


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Vertical position control:

The vertical position control moves the whole displayed trace upand down. It is used to set the no-input trace exactly on the centerline of the graticule, but also permits offsetting vertically by a limitedamount.Horizontal position control:

The horizontal position control moves the display sidewise. Itusually sets the left end of the trace at the left edge of the graticule,but it can displace the whole trace when desired. This control alsomoves the X-Y mode traces sidewise in some instruments, and cancompensate for a limited DC component as for vertical position.

Working of the cathode ray oscilloscope, CRO:

The electron gun is used to produce a narrow beam of electrons.It is heated when current flows through it. It is used to heat up thecathode. Heated cathode emits electrons through the process ofthermionic emissions. Grid controls the number of electrons in theelectron beams. The more negative the grid, the fewer the electronsare emitted from the electron gun and the less the brightness of the

bright spot on the screen. It focuses the electrons into a beam and toattract electrons from the area of the control grid. The acceleratoraccelerates the electron beam towards the screen. The deflectionsystem allows the electron beam to be deflected from its straight-linepath when it leaves the electron gun. Y-plates is to move the electronbeam vertically up and down the screen when an input voltage is appliedacross it. When no input voltage is applied, the electron beam does notdeflect and the bright spot is at the centre. When +ve voltage is

applied, the electron beam deflect upward. The bright spot moves tothe top. When -ve voltage is applied, the electron beam deflectsdownward.The fluorescent screen is coated on the inside surface with somefluorescent material such as phosphor or zinc sulfide. When electronbeam strikes the screen, the material becomes glows. This enables a


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bright spot to appear whenever an electron beam strikes the screen.The moving electrons have kinetic energy. When these electrons strikethe screen, the fluorescent coating on the screen converts the kineticenergy of the electrons into light energy.

Peak-to-Peak Voltage:

Voltage is shown on the vertical y-axis and the scale isdetermined by the Y AMPLIFIER (VOLTS/CM) control. Usually peak-peak voltage is measured because it can be read correctly even if theposition of 0V is not known. The amplitude is half the peak-peakvoltage.

If you wish to read the amplitude voltage directly you must check theposition of 0V, move the AC/GND/DC switch to GND (0V) and use Y-SHIFT (up/down) to adjust the position of the trace if necessary,switch back to DC afterwards so you can see the signal again.

Voltage = distance in cm volts/cmExample: peak-peak voltage = 4.2cm 2V/cm = 8.4Vamplitude (peak voltage) = peak-peak voltage = 4.2V

Frequency & Time period:

Time is shown on the horizontal x-axis and the scale isdetermined by the TIMEBASE (TIME/CM) control. The time period(often just called period) is the time for one cycle of the signal. Thefrequency is the number of cycles per second, frequency = 1/timeperiod

Ensure that the variable time base control is set to 1 or CAL(calibrated) before attempting to take a time reading.

Time = distance in cm time/cm


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2.Function Generator:A function generator is a piece of electronic test equipment orsoftware used to generate electrical waveforms. Thesewaveforms can be either repetitive or single-shot, in which casesome kind of triggering source is required (internal or external).Function Generators are used in development, testing and repairof electronic equipment, e.g. as a signal source to test amplifiers,or to introduce an error signal into a control loop.

A modern direct digital synthesis (DDS) function generator can

output a wide range of signals. Even a basic generator will outputsine, square and triangle waveforms, with variable amplitude andadjustable DC offset, ranging from less than 1 Hz to at least 1Hz. A wide variety of them also have other features, includingfrequency sweep, gated burst mode, AM and FM operation,variable symmetry and a higher frequency capability. Moreadvanced function generators, of course, output a wider varietyof waveforms.

Uses:

Basically, whenever you require a stable, repeatable stimulussignal, you use a function generator. They are used in a wide rangeof applications, including research and development, educationalinstitutions, electrical repair and hobbying, stimulus/responsetesting, in-circuit signal injection and frequency response

characterization.


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3.LCR MeterA LCR meter (Inductance (L), Capacitance (C), and Resistance (R)) is a

piece of electronic test equipment used to measure the inductance,capacitance and, resistance of a component. In the usual versions of

this instrument these quantities are not measured directly, but

determined from a measurement of impedance. The necessary

calculations are, however, incorporated in the instrument's circuitry;

the meter reads L, C and R directly with no human calculation required.

Usually the device under test (DUT) is subjected to an AC voltage

source. The meter detects the voltage over, and the current through

the DUT. From the ratio of these the meter can determine the

magnitude of the impedance. The phase angle between the voltage and

current is also detected and between that and the impedance

magnitude the DUT can be represented as an L and R or a C and R. The

meter must assume either a parallel or a series model for these two

elements. The most useful assumption, and the one usually adopted, is

that LR measurements have the elements in series (as would be

encountered in an inductor coil) and that CR measurements have the

elements in parallel (as would be encountered in measuring a capacitor

with a leaky dielectric).It can also be used to judge the inductance

variation with respect to the rotor position in permanent magnet

machines.


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Front-Panel Display

A 5-digit LED display shows measured values, entered parameters,

instrument status, and user messages. When making measurements, themajor parameter (L, C or R) is shown on the left display and the

appropriate minor parameter (Q, D or R) is shown on the right display.

Making Measurements

Measurements can be performed at test frequencies of 100 Hz, 120

Hz, 1 kHz, 10 kHz and 100 kHz (SR720 only). A built-in drive voltage

can be set to preset values (0.1, 0.25 and 1.0 V) or adjusted from 0.1 to

1.0 V in 50 mV increments.

Measurements are taken at rates of 2, 10 or 20 samples per second.

Consecutive readings can be averaged between 2 and 10 times for

increased accuracy. Both series or parallel equivalent circuit models of

a component are supported. Capacitor measurements use either the

internal 2.0 VDC bias or an external DC source of up to 40 volts.

Simple to Operate

The power and flexibility of the SR715 LCR meter and SR720 LCR

meter does not come at the expense of ease-of-use. A convenientAUTO measurement mode automates the selection of setup

parameters and quickly determines the appropriate device model for

whatever component is being measured. Up to nine instrument setups

can be stored in non-volatile memory for quick recall at a later time.


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3.Dual SuppliesSome electronic circuits require a power supply with positive and

negative outputs as well as zero volts (0V). This is called a 'dual supply'because it is like two ordinary supplies connected together as shown inthe diagram.Dual supplies have three outputs, for example a 9V supply has +9V, 0Vand -9V outputs.


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To Study the Equipments Used in the Semiconductor Lab