electronics assignment 3 - copy

8/13/2019 Electronics Assignment 3 - Copy

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Electronics Assignment 3

Ans1(a): 3

Ans 1(b): 3

Ans 1(c): 3

Ans 1(d): 3

Ans 1(e): 1

Ans 1(f): 4

Ans 1(g): 1

Ans 1(h): 3

Ans 1(i): 1

Ans 1(j): 3

Ans 2(a) Conductor:A conductor is a material which has a very high conductivitybecause of the presence of large number of free electrons.

Insulator: An insulator is a material that offers a very low level of conductivity underpressure from an applied voltage source.Semiconductor:A semiconductor, therefore, is a material that has a conductivity levesome where between the e!tremes of an insulator and a conductor. "he figure shows

the conduction and valence band for insulator, semiconductor and metals.

"he energy band gap in insulators is #E$% &A$'E. "he energy bands (#E$&A) in metals.


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"he energy band gap is semiconductor is larger than metals."he semiconductors have *

valence electrons.

Ans+b-Common mitter Configuration

"he Emitter is a common terminal between input and output. ere, the input is applied atbase and output is ta/en at the collector.

0ig 12

"he Input and (utput characteristics ,0or Common mitter npn "ransistor-"he input characteristics are a plot of the input current I - versus the input voltage

#E- for a range of values of output voltage #CE- as shown in fig 11.

0ig 11

0or the commonemitter configuration the output characteristics are a plot of the output

current IC- versus output voltage #CE- for a range of values of input current I-. As

shown in fig 1+, for a fi!ed value of I, as we increase the #CE, the collector current

increases. "he $egion to the right of #CEsat- is called saturation region. In this region

both the Emitter ase and Collector ase 4unctions are 0orward iased."he Input and(utput characteristics ,0or Common mitter pnp "ransistor-"he input characteristics are same as that for npn transistor, but here #E is replaced by

#E and #CEis replaced by #EC.In output characteristics, the #CE is replaced by #EC


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0ig 1+ "he output Characteristics of npn "ransistor in CE Configuration.Ans+c- &oad &ines&oad line is a tool to find the e!act current and voltage.Consider the 0ig.13. "he current through the resistor is

If I56 2, #56 #S

If #562, I56 #S7$

"he line which is s/etched by 4oining these two

)oints are called 5C &oad &ine shown in 0ig 1*- 0ig. 13

0ig 1*. 5C load line8 point 8 point is also called the operating point. "his is point of intersection of 5C&oad line and the #I Characteristics of a 5iode

Ans+d- C9(S Inverter


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C9(S stands for complementary 9(S C9(S-,which is a combination of n channel

and p channel 9(S0E"s. 0ig above shows a C9(S inverter.

(peration of C9(S inverter"he C9(S inverter input voltage is either high #55- or low2#-.;hen the input

voltage is high, 81 is off and 8+ is on. In this case, the shorted 8+ pulls the output

voltage down to ground.

;hen the input voltage is low,81 is on and 8+ is off. uals #557+.At this point, both

9(S0E"S have e>ual resistances and the output voltage e>uals #557+

Ans+e-


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As shown in table 1 the first type has an input voltage and an output voltage. "he circuit

that uses this type of negative feedbac/ is called a #oltageControlled #oltage Source#C#S-. A #C#S is an ideal voltage amplifier because it has a stabili=ed voltage gain,

infinite input impedance, and =ero output impedance.

In the second type of negative feedbac/, an input current controls an output voltage. "he

circuit using this type of feedbac/ is called a CurrentControlled #oltage SourceIC#S-. "his circuit is also /nown as transresistance amplifier.

"he third type of negative feedbac/ has an input voltage controlling an output current

"he circuit using this type is called a #oltageControlled Current Source #CIS-sometimes called transconductance amplifier.

In the fourth type, an input current is amplified to get a larger output current. "he circuit

is called a CurrentControlled Current Source ICIS-. An ICIS is an ideal currentamplifier because it has a stability current gain, =ero input impedance, and infinite

output impedance.

0ig13 ,a-#oltageControlled #oltage Source ,b- CurrentControlled #oltage Source

0ig1*,a-#oltageControlled Current Source ,b- CurrentControlled Current Source#C#S is a voltage amplifier and ICIS is a current amplifier where as IC#S is a current to

voltage and #CIS is a voltage to current amplifier.

Inpu

t

(utput Circuit Bin Bou

t

Converte

rs

$atio Symbol

# # #C#S 2 #out7#in Av

I # IC#S 2 2 i to v #out7Iin rm

# I #CIS v to i Iout7#in gm


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I I ICIS 2 Iout7Iin Ai

"able 10igure 13 a- shows the practical circuit of #C#S, the input impedance is not infinite but

it is very high. &i/ewise, the output impedance is not =ero, but it is very low. "he voltage

gain is symboli=ed by Av. 0igure 13 b- shows IC#S which has very low input and output

impedance. "he conversion factor of the IC#S is called transresistance rm-.

0igure 1* a- shows #CIS which has very high input and output resistance. "he

conversion factor #CIS is called transconductance gm-. 0igure 1* b- shows ICIS which

has very low input and very high output impedance. "he current gain is symboli=ed by Ai.

*.3 #C#S #oltage 'ain0igure 1? shows a


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Closed loop output impedance is given by

BoutC&- 6 $out7 1A#(&-

;here $out is the open loop output resistance.

"otal harmonic distortion is given by

"5C&

6 "5(&

7 1A#(&

-

;here "5(&is the open loop total harmonic distortion.

*.* "he IC#S Amplifier0igure 1@ shows a transresistance amplifier. It has an input current and an output

voltage. "he IC#S amplifier is an almost perfect currenttovoltage converter because it

has =ero input impedance and =ero output impedance.

0ig 1@ IC#S amplifier"he e!act e>uation of the output voltage is given by

(utput voltage is given by

#out6 iin$f-

"he circuit is a voltage converter by ta/ing different values $f we can very the output

voltage.

"he e!act e>uation of the output voltage is given by

Input and output impedances are given by

*.? "he #CIS Amplifier


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0ig 1 #CIS amplifier0igure 1 shows a transconductance amplifier. It is similar to a #C#S amplifier, e!cept

that $&is the load resistor as well as the feedbac/ resistor. "he active output is not the

voltage across voltage across $& $1F rather, it is the current through $&.

"he output current is given by

iout6 vin7 $1

iout6 vingm

"he e!act output current is given by

"he circuit is a voltagetocurrent converter . "he input and output impedances are given

by

*.@ "he ICIS Amplifier

0ig 1G ICIS amplifierAn ICIS circuit amplifies the input current. ecause of the heavy negative feedbac/, the

ICIS amplifier tends to act li/e a perfect current amplifier. It has very low input and very

high output impedance. "he closed loop current gain is given by


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"he input and output impedances are given by

Ans+f- 5#9: "he first digitalvoltmeter was invented and produced by Andrew Hayof

uantity to a digital number that

represents the >uantityJs amplitude. "he conversion involves >uanti=ationof the input, so

it introduces a small amount of error. "he inverse operation is performed by a digitalto

analog converter5AC-. Instead of doing a single conversion, an A5C often performs the

conversions KsamplesK the input- periodically. "he result is a se>uence of digital values

that have converted a continuoustime and continuousamplitude analog signalto a

discretetime and discreteamplitude digital signal. An A5C may also provide an isolated

measurement such as an electronicdevice that converts an input analog voltageorcurrentto a digital number proportional to the magnitude of the voltage or current.

owever, some nonelectronic or only partially electronic devices, such as rotary

encoders, can also be considered A5Cs."he digital output may use different coding

schemes. "ypically the digital output will be a twoJs complementbinary number that is
http://en.wikipedia.org/wiki/Andrew_Kayhttp://en.wikipedia.org/wiki/Kayprohttp://en.wikipedia.org/wiki/Analog-to-digital_converterhttp://en.wikipedia.org/wiki/Integrating_ADChttp://en.wikipedia.org/wiki/Voltage_referencehttp://en.wikipedia.org/wiki/Weston_cellhttp://en.wikipedia.org/wiki/Quantization_(signal_processing)http://en.wikipedia.org/wiki/Digital-to-analog_converterhttp://en.wikipedia.org/wiki/Digital-to-analog_converterhttp://en.wikipedia.org/wiki/Sampling_(signal_processing)http://en.wikipedia.org/wiki/Analog_signalhttp://en.wikipedia.org/wiki/Digital_signalhttp://en.wikipedia.org/wiki/Electronicshttp://en.wikipedia.org/wiki/Voltagehttp://en.wikipedia.org/wiki/Electric_currenthttp://en.wikipedia.org/wiki/Rotary_encoderhttp://en.wikipedia.org/wiki/Rotary_encoderhttp://en.wikipedia.org/wiki/Two's_complementhttp://en.wikipedia.org/wiki/Andrew_Kayhttp://en.wikipedia.org/wiki/Kayprohttp://en.wikipedia.org/wiki/Analog-to-digital_converterhttp://en.wikipedia.org/wiki/Integrating_ADChttp://en.wikipedia.org/wiki/Voltage_referencehttp://en.wikipedia.org/wiki/Weston_cellhttp://en.wikipedia.org/wiki/Quantization_(signal_processing)http://en.wikipedia.org/wiki/Digital-to-analog_converterhttp://en.wikipedia.org/wiki/Digital-to-analog_converterhttp://en.wikipedia.org/wiki/Sampling_(signal_processing)http://en.wikipedia.org/wiki/Analog_signalhttp://en.wikipedia.org/wiki/Digital_signalhttp://en.wikipedia.org/wiki/Electronicshttp://en.wikipedia.org/wiki/Voltagehttp://en.wikipedia.org/wiki/Electric_currenthttp://en.wikipedia.org/wiki/Rotary_encoderhttp://en.wikipedia.org/wiki/Rotary_encoderhttp://en.wikipedia.org/wiki/Two's_complement


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proportional to the input, but there are other possibilities

Section CAns 3,a- : "he Cho/e Input 0ilterCho/e Input 0ilter 0ig +- are used to filter the ouput of a $ectifier."he Cho/eor

inductor- has a primary charcterisitcs of opposing a change in current.ecause of this,a

cho/e Input filter ideally reduces the A.C current in the load resistor to =ero.

0or designing a cho/e input filter ,we have two re>uirements.

1. Cho/e Input filter should LCvalue much smaller than $&at the input fre>uency.;hen

this re>uirement is satisfied,we can ignore the load resistance $&.+. ;e should have L& much greater than LCat the input fre>uency.;hen this condition is

satisfied ,the ac output voltage approaches =ero.

0ig.+,a- Cho/e Input filter ,b- AC E>uivalent Circuit

0iltering the (utput of a $ectifier"he easiest way to understand the filtering operation is by using the superposition

theorem.

"he Superposition "heorem states that if we have two of more sources,we can analyse

the circuit for each source separately and then add the individual voltages to get the

total voltage0ig +G-.


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"he $ectifier output has two different components: a 5.C voltage the average value- and

an A.C voltagethe fluctuating part-.

;hen A.C voltage is concerned,the inductive reactance is =ero and capacitive reactance

is infinite."hus ,almost all the 5C component is passed on to the load resistor and almost

all the AC component is bloc/ed.

In this way, we get almost perfect 5C voltage."he only deviation is small AC load

voltages called $ipple.

0ig+G,a-$ectifier with Cho/e Input 0ilter ,b-$ectifer (utput has 5C and AC components

,c-5C E>uivalent Circuit ,d- 0ilter output is direct current with small ripple.

"he Capacitor Input 0ilter"he Cho/e Input 0ilter produces a 5C output voltage e>ual to the average value of the

rectified voltage."he capacitor input filter produces a 5C output voltage e>ual to the

pea/ value of the rectified voltage."his 0ilter is most widely used in power supplies.

Capacitor Input 0ilter with


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0or the capacitor input filter to be constant, we need to connect a load resistor across

the capacitor. As long as $&C time constant is much greater than the period, capacitor

remains almost fully charged and the voltage appro!imately #).

"he only deviation from perfect 5C voltage is small ripple. "he smaller the pea/ to pea/

value of this ripple, the more closely the output approaches a perfect 5C voltage.

etween the pea/s, the diode is off and the capacitor discharges through the load

resistor. Since the capacitor discharges only slightly between pea/s, the pea/ to pea/

ripple is small.

0ig.32 ,a- &oaded capacitor input filter ,b- (utput is direct current with small ripple,c-0ull wave output has less ripple.

Surge Current

0ig.31Surge $esistor limits surge current.;hen the power is turned on,the filter is uncharged.At the first instant,when the power is

applied,the capacitor loo/s li/e a short circuit."he initial charging current may be very

large.All that e!ists in the charging path to impede the current is the resistance of the

transformer winding and the bul/ resistance of the diodes.

"he initial rush of current when the power is turned on is called the SM$'E CM$$E


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;e have to solve this e!ample using the same steps discussed in above e!ample.Ans

Ans *: A ipolar Nunction "ransistor N"- is a three terminal device whose operation is

dependent on the interaction of both ma4ority and minority carriers and hence it is called

bipolar device. "ransistor means transfer of resistor i.e, transfer of resistance from low

resistance input -to high resistance output- circuit.

Construction of a N"1. npn : "he n D p Dn transistor is formed by sandwiching a thin OpP type semiconductorbetween two OnP type semiconductors.0ig 1-ase comes between collector and emitter

region. ase is thin and lightly doped. 5oping level of Emitter is intermediate between

Emitter and ase .Emitter and collector are much wider than base and are heavily doped.

"he emitter is heavily doped than the collector.

0ig 1

0ig @Applying HC& ,we obtain IE 6 I IC

Alpha 5.CQdc-6 IC7IE , eta 5.C Rdc- 6 IC7I


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Ans ?: < channel enhancement Dtype 9(S0 ""he basic construction of the nchannel enhancementtype 9(S0E" is provided in 0ig.1

A slab of ptype material is formed from a silicon base and is referred to as the

substrate. As with the depletiontype 9(S0E", the substrate is sometimes internally

connected to the source terminal, while in other cases a fourth lead is made available for

e!ternal control of its potential level. "he source and drain terminals are connected

through metallic contacts to ndoped regions, but note in 0ig.1 the absence of a channel

between the two ndoped regions. "his is the primary difference between the

construction of depletiontype and enhancementtype 9(S0E"sthe absence of a

channel as a constructed component of the device. "he Si(+ layer is still present to

isolate the gate metallic platform from the region between the drain and source, but now

it is simply separated from a section of the ptype material. In summary, therefore, the

construction of an enhancementtype 9(S0E" is >uite similar to that of the depletion

type 9(S0E", e!cept for the absence of a channel between the drain and source

terminals.

0ig 1

asic (peration1. (peration with #'S62# and #5S6 positive.If #'S is set at 2 # and a voltage applied between the drain and source of the device of

0ig.1, the absence of an nchannel with its generous number of free carriers-will result

in a current of 2 Amperes.

+. (peration with #'S6 positive and #5S6 positive.In 0ig. + both #5S and #'Shave been set at some positive voltage greater than 2 #

establishing the drain and gate at a positive potential with respect to the source."he


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positive potential at the gate will pressure the holes since li/e charges repel- in the p

substrate along the edge of the Si(+ layer to leave the area and enter deeper regions

(f the psubstrate, as shown in the figure. "he result is a depletion region near the Si(+

insulating layer void of holes. owever, the electrons in the psubstrate the minority

carriers of the material- will be attracted to the positive gate and accumulate in the

region near the surface of the Si(+ layer. "he Si(+ layer and its insulating >ualities will

prevent the negative carriers from being absorbed at the gate terminal. As #'S increases

in magnitude, the concentration of electrons near the Si(+ surface increases until

eventually the induced ntype region can support a measurable flow between drain and

source.

"hreshold #oltage #" "he level of #'Sat which the channel begins to conduct is calledthe "hreshold #oltage, #". Since the channel is none!istent with #'S 6 2 # and

TenhancedU by the application of a positive gatetosource voltage, this type of 9(S0E"

is called an enhancementtype 9(S0E".

0ig +As #'Sis increased beyond the threshold level, the density of free carriers in theinduced

channel will increase, resulting in an increased level of drain current. owever,if we hold

#'Sconstant and increase the level of #5S, the following conditions results.

1. If #'S #5SV #", the n channel 9(S0E" will wor/ in &inear $egion, and the drain

current I5will increase linearly with increase in drain voltage #5S.

+. If #'S #5S6 #", the gate will become less and less positive with respect to drain. "hus,

the number of electrons near to the drain terminal also reduces and channel will be

become )I


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3. If #'S #5S V #",the n channel 9(S0E" will enter into SA"M$A"I(


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#CC

#1Inverting input

#+ uencies. Its reliability, stability, and ease of operation ma/e it suitable as a

general purpose laboratory instrument. "he heart of the C$( is a cathoderay tube shown

schematically in 0ig. 1.


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electronics assignment 3 - copy

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