Chapter 1 VOLTAGE REGULATOR [Compatibility Mode]

5/19/2018 Chapter 1 VOLTAGE REGULATOR [Compatibility Mode]

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SEE 3263SEE 3263

ELECTRONIC SYSTEMSELECTRONIC SYSTEMS

1

DR. RUBITA [email protected]: 07- 5535270

C 1:C 1:

SEE 3263: ELECTRONIC SYSTEMS

2

1.0

.

.

.

A .

E 240, 50H

.

A , .

A

.

F ( )

.

.

A .


2/26

DC POWER SUPPLY BLOCK DIAGRAM

5

/

6

These power supplies were constructed using

discrete components, integrated circuits or

combination of both.

7

Discrete power transistor, op-amp and

comparator were used to complete the circuit.

POWER SUPPLY REGULATION

An ideal power supply provides a

constant dc voltage despite changes tothe input voltage or load conditions.

8

The output voltage of a real powersupply changes under load and is alsosensitive to input voltage changes.


3/26

VOLTAGE REGULATION

2 basic categories:

(i) Load Regulation - Output voltagenearly constant when load change.

9

(ii) Line Regulation - Output voltagenearly constant when line voltage

change.

Load regulationLoad regulationis a measure of how well apower supply is able to maintain the dc output

voltage between no load and full load with the

input voltage constant.

LOAD REGULATION

10

,

when load current increases.

VO(NL) output voltage with no

load.

VO(FL) output voltage with fullload.

IL(FL) full load current (maximum

current that coming out

from power supply).

Load regulation can be expressed as a

percentage change in load voltage.

Load Regulation = %100V

VV

)FL(O

)FL(O)NL(O

Load re ulation can also be ex ressed in terms

11

of percent change in the output per mA changein load current (%/mA).

%100II

V

VV

%100I

V

V

VL(NL)L(FL)

O(FL)

O(FL)O(NL)

L

O

O

reg

=

=

EXAMPLE:

A regulated power supply with an output resistance of 1 deliver a full load current of 1A to a 25 load. What is the

load regulation?


4/26

V25)25)(A1(RIV L)FL(L)FL(O ===

13

)NL(O)NL(O

OL

L)FL(O V

125

25V

RR

RV

+=

+=

V26V)NL(O =

%4%10025

2526%100

V

VVV%

)FL(O

)FL(O)NL(O

reg =

=

=

.

LINE REGULATION

14

() ,

.

Line regulation can be expressed as:

LINE REGULATION

%100V

V

i

O

Line Regulation =

15

%100V

VV

i

O

O

Line regulation can also be expressed in termsof percent change in VO per volt change on the

Vi (%/V).

Line Regulation =

5, 0.25.

15. D

%/.

:

F ,

(0%).

V/%333.0%100V5

V15.

=Line Regulation =


5/26

ZENER REGULATOR

17

>

&

,

,

EALE:D:

() I() I() .

() D() D() .() , , .

mA45.512

mA60R

VIIII

(min)L

OS(max)LS(min)Z ====

220

mA4012

mA60V

IIII OS(min)LS(max)Z ====

mA60100

1218IS =

=

=

S

Oi

R

VV

(max)L

mW480)12)(mA40(VIP Z(max)Z(max)DZ ===

mW36.0100)mA60(R)I(P 2S2

SRS ===

19

mW4.65)12)(mA45.5(VIP Z(min)Z(min)DZ ===

() .

()

.2 .

20


6/26

EECIE:F ,

.

G: = 5.1 I= 35 A

IK= 1 A, = 12 , I= 70 A

21

.

III LE ==

)1()1( ++

)1(

II-III LSBSZ

+==

BEZO -VVV =

EXAMPLE 1.4 (pg 1-14):If = 50, determine:(a) output voltage, VO (b) voltage, VCE1(c) current, IS (d) current, IZ

(b) Vi = VCE + VOVCE = Vi VO = 20 11.35 = 8.65 V

23

i = S S Z

IS = = = 0.04 A

(d)

= 39.78 mA

S

Zi

R

VV

200

1220

A55.222mA40III

A55.222

51

mA35.11

1

I

1

II

mA35.11k1

V35.11

R

VI

BSZ

LEB

L

OL

==

==

+

=

+

=

===

(a) VO = VZ VBE =12 0.65 = 11.35 V

DP

L

DP

1E2B III

=

=

A Darlington pair transistor (a very high DC) can beused to increase the current gain. This will reducethe base current and the zener power rating will below.

24

BEZO

DP

LS

2BSZ

2121DP

V2VV

II

III

=

=

=

++=


7/26

Design a Darlington series-pass voltage regulatorlike that of figure shown below from the followingrequirements: VDC(in) = 18V, VDC(out) = VE = 12V, IL(max) =2A.

25

EGLA CICI IH FEEDBACKEGLA CICI IH FEEDBACKQ1

Q2

R4

R1

RL

IL

I4

IB1

IC2 - VZ +VIN +VO

VRR

RV

VRR

RV

VVV

2

21

2O

O

21

22

Z2BE2

+=

+=

+=

R3R2

B2 +VBE2

-

+V2-

VB1 = VCE2 -

26

)VV(R

R1V Z2BE

2

1O +

+=

Any change in VO must cause a change in VBE1 to maintainthe equality. If VO decreases, VBE1 must increase since VZis constant. Similarly if VO increases, VBE1 must decrease.

ILE EIE LAGE EGLAILE EIE LAGE EGLA

BLCK DIAGABLCK DIAGA

CONTROL

ELEMENTVIN VOUT

REFERENCE

VOLTAGE

ERROR

DETECTOR

SAMPLE

CIRCUIT

27

Series Regulators

Series Regulator block diagram:

Basic series re ulator circuit:

VIN VOUT

Error

detector

Sample

circuit

Control

element

Reference

voltage

28

VIN VOUT

R1

Control element

Q1

D1

VREF+

Error detector

R2

R3

Sample

circuit

The control elementmaintains a constant outputvoltage by varying the

collector-emitter voltageacross the transistor.


8/26

BAIC BAIC A EIE EGLAA EIE EGLA

+

Q1

R2R1

RL

IL

V+ =VZ

VIN+

-R3

+

VZ-

V- O

-

29

Z

3

2O V

RR1V

+=

VR

R1V Z

2O

+=

EALE:F :

() ?

() I 200A, 1?

( )

W16.1

)A2.0(V2.12V18VIP

=

==

30

V2.12

V9.3k47

k1001

=

+=

ECI CICIECI CICI

2 :

1. /

2.

LIEA CE LIIIG CICILIEA CE LIIIG CICI

32

I

L() . I

L> I

L(),

IL IL(). IL

L .


9/26

33

. 2

0. 2 .

1,

..SC

(max)LR

V7.0I =

The currentlimit is:

EXAMPLE:

34

A A

25 . , 25 . , CC , I , IL()L() 0.5 A? 0.5 A?

CC, , LL= 100= 100 LL= 10= 10??

FLDBACK CE LIIIGFLDBACK CE LIIIG

CICICICI

35

D = 0 IL= IC,

D=()IC= (20 0)1A= 20 ( )

D

=(

)IC

= (20 0)0.5A=10 ( )

D = 15 IL= 1 A,

36

D= ()IL= (20 15)1 A = 5 ( )

D ,

20 1

. 10 .


10/26

EIE EGLA IH FLDBACKEIE EGLA IH FLDBACK

CE LIIIGCE LIIIG

37

FoldFold--back current limitingback current limitingdrops the load current wellbelow the peak during overload conditions. Q2 conductswhen VR4 + VBE2 = VRSC and begins current limiting.

VBE2 = VRSC VR4

VR4 will increase or decrease if VO increases ordecreases. At this instant, Q2 is still not conducting. VR4 isfound by applying the voltage-divider rule:

( )ORSC54

44R VV

RR

RV +

+=

38

When IL increase to IL(max) or during overload, VR4 will dropbecause VO drops. A smaller value of VRSC is required tomaintain VBE2 0.7V. This means that less current isneeded to maintain conduction in Q2 and the load current

drops.

At this point, current limiting occurs. IL will be limited and Q2conducting (ON).

39

If the regulated output voltage is 10 V, determine:

(a) The short circuit current, ISC(b) The maximum load current, IL(max)(c) Power dissipation in transistor 2N3055 during shorted load.

Q1Vi =23V

R11.2

RSC

Test Question Example:For the circuit shown below, determine :(a) Maximum load current.(b) Output voltage range.(c) Values of VB1 and IR2 if RL = 10 and VO = 15 V.

40

Q2

Q3

VZ =10V

R23k

R33.3k

R45k

R510k

RL

IR2

B1


11/26

Final Exam Question Example:

41

A series voltage regulator circuit above produce an output voltage, VO =10 V and a maximum load current, IL(max) = 1 A. Given for all transistors,Q1, Q2, and Q3 : = hFE = 100, VBE(ON) = 0.7 V; for Zener diode, DZ : VZ =4.3 V, rZ = 0 , IZK = 1 mA and IZM = 40 mA. The unregulated inputvoltage, Vi is 20 V. During optimum operation, I1=2 mA, IZ = 14 mA, I3 =1 mA and IB3 can be neglected.


42

Draw a basic block diagram for this regulator circuit.Sketch an label clearly the graph of VO versus IO.

Briefly explain how the output voltage, VO is maintain constant evenwhen the input voltage, Vi varies within the permitted range.


43

Explain the function of resistors, R1 and R2.

Determine the resistor value of R1 and R2.

Determine the resistor value of R3 and R4.

Determine the suitable range value of RL.


44

Determine the power dissipation in Q1, Q2 and DZ at Optimumoperation.

The pass transistor Q1 will easily burnt when load RL is shorted.Suggest one circuit that can be used to overcome the problem.Briefly explain how this additional circuit works.


12/26

SHUNT-TYPE VOLTAGEREGULATOR BLOCK DIAGRAM

45

Shunt Regulators

Shunt Regulator block diagram:

VIN

R1

VOUT

ControlErrorReference

46

Basic shunt regulator circuit:e ement(shunt)

Samplecircuit

detectorvoltage

VIN

VOUT

R2

Q1

+

D1

R4

R3 RL

VREF

Error detectorControl

element

Sample

circuit

R1

The control elementmaintains a constant outputvoltage by varying thecollector currentin thetransistor.

H LAGE EGLAH LAGE EGLA

IH IH AA

Shunt regulators use a

parallel transistor for the

control element. If the output

47

Although it is less efficient than the series regulator, the

shunt regulator has inherent short-circuit protection. The

maximum current when the output is shorted is VIN

/R4.

voltage changes, the op-amp

senses the change and

corrects the bias on Q1. A

decrease in output voltage

causes a decrease in VB

and

an increase in VC.

SWITCHING REGULATORS

To reduce power dissipation in pass transistor.

Gives higher efficiency.

Able to supply very large load current with lowvoltage as required in the PC.

48

step-down

step-up

inverting

Step-down switching regulator is widely used as

the power supply in PC.


13/26

Switching Regulators

All switching regulators control the output voltage byrapidly switching the input voltage on and off with a dutycycle that depends on the load. Because they use highfrequency switching, they tend to be electrically noisy.

49

VC

ton toff ton toff ton toff tonon/offcontrol

VOUT


All switching regulators control the output voltage byrapidly switching the input voltage on and off with a dutycycle that depends on the load. Because they use highfrequency switching, they tend to be electrically noisy.

50

ton toff ton toff ton toff ton

VC

on/offcontrol

VOUT

An increase in the duty cycle increases the output voltage.


All switching regulators control the output voltage byrapidly switching the input voltage on and off with a duty

cycle that depends on the load. Because they use highfrequency switching, they tend to be electrically noisy.

51

VC

ton toff ton toff ton toff tonon/offcontrol

VOUT

A decrease in the duty cycle decreases the output voltage.

BASIC SWITCHING REGULATOR

R1+

Vi

Q 1

Gated

Latch

R 3

I L

C

L

D1PWM

52

L o

-

+

-

V2+

-Pengayun

+

-V

Z

R2

Vralat


14/26


15/26

57

=

=

T

TVV

T

TCycleDuty

HIHIdc

HI

EXAMPLEBy assuming an ideal LC,By assuming an ideal LC,(a)(a) Explain the function of PWM, DExplain the function of PWM, D11, L and C., L and C.(b)(b) Explain the operation of the circuit if VExplain the operation of the circuit if VOUTOUT decreases.decreases.

(c)(c) Calculate VCalculate VOUTOUT..(d)(d) If VIf Vii increase to15 V, sketch the waveform at point Bincrease to15 V, sketch the waveform at point B

in order to maintain the value found inin order to maintain the value found in (c).(c).

58

59

PWM is used to produce pulse trains with pulse width depend on thePWM is used to produce pulse trains with pulse width depend on thechanges in output, Vchanges in output, VOUTOUT. These pulse trains (at point B) will control the ON. These pulse trains (at point B) will control the ONand OFF interval of Qand OFF interval of Q11 thus will finally increase or decrease the value ofthus will finally increase or decrease the value ofVVOUTOUT..

The diode DThe diode D11 is used to eliminate the negative voltage.is used to eliminate the negative voltage.

Inductor, L and capacitor, C is used as filter to average the switchedInductor, L and capacitor, C is used as filter to average the switchedvoltage thus producevoltage thus produce VVDCDC..

60

When VOUT reduced, VR2 will also reduced thus Verror will increase becauseVZ is constant.PWM will produce pulse trains with large pulse width.Q1 will ON and OFF with large duty cycle thus increase the dc currentflowing through it.

The increase of dc current in Q1 will then increase the VOUT that try toreduce previously.This regulating action maintains VOUT at an essentially constant level.


16/26

61

V5.712m6m10

m10V

TT

TV i

OFFON

ONOUT =

+=

+=

msT

m

T.

V

T

TV

ON

ON

iON

OUT

8

1516

57

=

=

=

8 ms

8 ms

ICHIG EGLA IHICHIG EGLA IH

CCI CCI

CC , , EEAD AD

LAGELAGE

VERROR

VOSC

VAT

VH

V1

+

(V )

-

(V )

TON

VOSC

VH

V1

-

(V )

VERROR

+

(V )

VDC

TON

+T

OFF

TON

TON

+T

OFF(a)

(b)

0

0 t

t

PWM GENERATION USING SAWTOOTHGENERATOR AND VOLTAGE COMPARATOR

64


17/26

:

Higher efficiency.Higher efficiency.

Light and compact.Light and compact.

Filtering is easy to achieve at high frequencies.Filtering is easy to achieve at high frequencies.

VVOO VVii

65

Generate EMI (Generate EMI (electromagnetic interferenceelectromagnetic interference) where switching at high) where switching at high

frequency for Qfrequency for Q11 current will produce large magnetic fields whichcurrent will produce large magnetic fields which

induced noise voltage around conductor.induced noise voltage around conductor.

Limited performance of power transistor (pass transistor) to switchLimited performance of power transistor (pass transistor) to switch

ONONandand OFFOFFat high speed.at high speed.

Contain large noise and ripple in VContain large noise and ripple in VOO..

Vi

Series

Element

Protection

Circuit Vo

66

Comparator

Amplifier

Reference

VoltageSampling

Circuit

IC voltage regulators are available asseries regulators or as

switching regulators. The popular three-terminal regulators areoften used on separate pc boards within a system because theyare inexpensive and avoid problems associated with large powerdistribution systems (such as noise pickup).

IC EGLA 78 EIEIC EGLA 78 EIEThe only external components required with the 78XX seriesare input and output capacitors and some form of heat sink.

These IC include thermal shutdown protection and internal

current limiting.

The 78XX series is a fixed positive outputregulator available in various packagesand with standard voltage outputs.

They are primarily used for fixed outputvoltages, but with additional components,they can be set up for variable voltages orcurrents.

DD--PAKPAK TOTO--220220

TOTO--33

IC EGLA 78 EIEIC EGLA 78 EIE

11 33

22

- Can produce output current in excess of 1A

- VIN must be at least 2V- 3V above the output voltage

- C1 to prevent from unwanted oscillation

- C2 act as a line filter to improve transient response

Type number Output voltage

7805

7806

7808

7809

78127815

7818

7824

+5.0 V

+6.0 V

+8.0 V

+9.0 V

+12.0 V+15.0 V

+18.0 V

+24.0 V


18/26

IC EGLA 79 EIEIC EGLA 79 EIE

22 33

11

The 79XX series is the negativeoutput counterpart to the 78XX

series, however the pin assignmentsare different on this series.

Other specifications are basicallythe same.

7905

7905.2

79067908

7912

7915

7918

7924

5.0 V

5.2 V

6.0 V8.0 V

12.0 V

15.0 V

18.0 V

24.0 V

Type number Output voltage

LIEA IC EGLA L317LIEA IC EGLA L317

R1

+VOUT+VIN LM317

IREFVREF1

23

+ve output regulator

The LM317 is an adjustable positive output IC regulator.There is a fixed reference voltage of +1.25 V between theoutput and adjustment terminals. There is no ground pin.

R2IREF+ IADJ

IADJ

70

2ADJ

1

2REFOUT RI

R

R1vV +

+=

VREF = 1.25V

Maximum Current 1.5A

Output may varies 1.2V 37V

Input voltage 4V 40 V

The output voltage is calculated by:The output voltage is calculated by:

The LM337 is an adjustable negative output IC regulator.

Example:What is the value of VOUT? (Assume IADJ is 50 A):

V

kAk

VVOUT

02.18

)2)(50(

150

2125.1

=

+

+=

71

IC EGLA IH BE CEIC EGLA IH BE CE

VINQext

IC regulators are limited to a maximum allowable currentbefore shutting down. The circuit shown is uses anexternal pass transistor to increase the maximumavailable load current.

Rext sets the

RL

VOUT78XX

RextC1

C2

72

point whereQext begins toconduct:

max

extI

V7.0R =


19/26

IC EGLA IH EEALIC EGLA IH EEAL

CE LIIIG CICICE LIIIG CICI

VOUT

VIN

78XX

Qext

Rext

Rlim

Qlim

RL

73

Previous slide shows that the external transistor is not

protected from excessive current, such as would resultfrom a shorted output. An additional current-limitingcircuit (Qlim and Rlim) can be added to protect Qext fromexcessive current and possible burn out.

EALEEALE

An IC voltage regulator shown below is able to operatewith a much higher output current, IL. If given VEB1(ON) =V

EB2(ON)= 0.7 V, I

O(max)= 1A and

1= 15:

(a) Explain the function of transistors Q1 and Q2.(b) Determine IC1 and IO when RL = 100 and 1 .

(a) Explain the function of transistors Q1 and Q2.

Q1 act as an external pass transistor to handle excesscurrent that is unable to be handled by three-terminalIC regulator.

Q2 act as the current limiting circuit to protect Q1 fromexcessive maximum current.

(b) Determine I and I when R = 100 and 1 .

IR1

IB1

When VEB1


20/26

When RL = 100 and 1 , the values of IC1 and IO can

be found as tabulated in the table below.

L L B1 C1 O

100 50 mA 0A 0A 50 mA

1 5000 mA 297.92 mA 4468.8 mA 531.2 mA

77

A CE EGLAA CE EGLA

V

IC regulators can be used as a current source when anapplication requires that a constant current can be

supplied to a variable load. R1 is the current-settingresistor.

R1

RL

IOUT

ILIG

VOUTGND PIN

78

G

1

OUTL IR

VI +=

E L IH E L IH

EIAL LAGEEIAL LAGE

7815In Out

GndC1

10 uF20V

4000 uF30V

240V

50 Hz

C2

VO1

24V

24V

79

7915In Out

GndC

3 C

4

10 uF

20V

4000 uF

30V

N1

N2

:

VO2

IC Voltage Regulators

The 78S40 is an IC containing all of the elements neededto configure a switching regulator, using a few externalparts.

It is a universal switchinguniversal switchingre ulator subs stemre ulator subs stem

VINCT

CS

VCC

Noninvert

input

Invert

input Gnd

Timing

capVCC

Ipksense

Driver

collector

Switch

collector

80

because it can be configuredas a step-down, step-up, orinverting regulator by theuser. The data sheet showstypical circuits for theseconfigurations.

+

10 11 12 13 14 15 16

7 6 5 4 3 2 1

+

Q1

Q2

SOscillator

R

Q

Comp.

Flip-flop

VOUT

R1

L

CO

R2

1.25 Vreference

D1

8

9

+

9 10 11 12 13 14 15 16

8 7 6 5 4 3 2 1

Referencevoltage

Invertinput

Noninvertinput

VCCop-amp

Output Switchemitter

Anode Cathode

+

Q1

Q2

SOscillator

R

Q

Comp.

Flip-flop

1.25 Vreference

D1

Here is the step-downconfiguration.


21/26

81 82

EIE LAGE EGLA IH CAEIE LAGE EGLA IH CA

CE LIIIG IG L 723CE LIIIG IG L 723

723


22/26

Regulator

Line regulation

A

.

() .

SummarySummarySummary

Load regulation

Linear regulator

Switchingregulator

.

A

.

A

.

DEADIG EIDEADIG EI

The load regulation of an ideal power supply is

________.

(a) 0%(a) 0%

(b) 25%

(c) 50

(d) 100%

(e) none of the above

DEADIG EIDEADIG EI

An AC-DC converter power supply contains all of thefollowing except a ________.

(a) rectifier circuit

(b) filter circuit

(c) sample-and-hold circuit

(d) regulator circuit


(c) sample-and-hold circuit

DEADIG EIDEADIG EI

The ideal voltage regulator maintains a constant DCoutput voltage regardless of changes in __________.

(a) its input voltage

(b) its output voltage demand

(c) its load current demand

(d) both (a) and (c)


(d) both (a) and (c)


23/26

DEADIG EIDEADIG EI

Under full load condition, ___________.

(a) the input voltage is at its maximum value

(b) the load resistance is at a minimum value

(c) no load resistance is present

(d) the load current is at a minimum value


(b) the load resistance is at a minimum value

DEADIG EIDEADIG EI

__________ is a measurement of how well thepower supply maintains a constant voltage across

the load with changes in load current.

(a) Voltage control

(b) Load voltage control

(c) Load regulation

(d) Line regulation


(c) Load regulation

DEADIG EIDEADIG EI

What is the load regulation of a power supply with ano load voltage of 16.5 V and a full load voltage of15 V?

(a) 1.5%

(b) 9.1%

(c) 10%

(d) 90.9%


(c) 10%

DEADIG EIDEADIG EI

__________ is a measurement of how well thepower supply maintains a constant output voltagewith changes in input voltage.

(a) Voltage control

(b) Load voltage control

(c) Load regulation

(d) Line regulation


(d) Line regulation


24/26

DEADIG EIDEADIG EI

The pass transistor in linear regulators will_________.

(a) operate in the linear area at all times(a) operate in the linear area at all times

(b) be in cutoff at all times

(c) be in saturation at all times

(d) switch between cutoff and saturation


DEADIG EIDEADIG EI

Switching regulators have _________ than linearregulators.

(a) longer life

(b) simpler circuitry

(c) a higher cost in all cases

(d) greater efficiency


(d) greater efficiency

A correct formula for load regulation is _________.

OUT

INLoad Regulation = 100%

V

V

a.

95

( )OUT OUT

IN

/ 100%Load Regulation = V VV

d.

FL

NL FL

Load Regulation = 100%V

V V

c.

NL FL

FL

Load Regulation = 100%V V

V

b.

(a) output resistance and the full-load

An alternate way to express load regulation is interms of the _________.

(a) output resistance and the full-load

res s ance

(b) output resistance and the shorted-loadresistance

(c) input resistance and the full-load resistance

(d) input resistance and the shorted-loadresistance

res s ance

96


25/26

a 0.5 A VIN VOUTQ1 R4

In the circuit shown, R4 = 0.7 . The output currentwill be limited to _________.

(b) 0.7 A

(c) 1.0 A

(d) 1.4 A

R1

R3

R2

Q2

Current limiter

+

0.7

(c) 1.0 A

97

(a) control element

The block diagram for a series voltage regulator isshown. The yellow box represents a _________.

(b) sample circuit

(c) error detector

(d) reference voltage

IN OUT

?

98


(a) control element VIN

R1

VOUT

The block diagram for a shunt voltage regulator isshown. The yellow box represents a _________.

(b) sample circuit

(c) error detector


?

99

(b) sample circuit

(a) high speed switching circuit(b) fold-back current limiter

The circuit in the blue shaded area is a _________.

(b) fold-back current limiter

(c) reference source

(d) shunt regulator+VIN VOUT

R1

Q1

+

Q2

R4

D1

R3

R2

R6

R5

100


26/26

a low noise

A major advantage of all switching regulators is

_________.

(b) high output impedance

(c) high efficiency

(d) all of the above

101

(c) high efficiency

(a) series linear

+VIN

VOUTQ1 D1

on

offC+VIN

VOUTQ1 D1

on

off+VIN

VOUTQ1 D1

The type of regulator circuit shown is a _________.

(b) series switching

(c) shunt switching

(d) none of the above

R1

R3

R2 RL

D2

Variable

pulse-width

oscillator

L

+

C+

L fieldbuilds

esR1

R3

R2 RL

D2

Variable

pulse-width

oscillator

L

+

C

L fieldcollapses

+Ccharges

R1

R3

R2 RL

D2

Variable

pulse-width

oscillator

L

+

C

102

(d) none of the above

(a) +5 V

The output voltage from a 7912 is a regulated_________.

(b) +12 V

(c) 5 V

(d) 12 V

103

() 12 V

104

Chapter 1 VOLTAGE REGULATOR [Compatibility Mode]

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Transcript of Chapter 1 VOLTAGE REGULATOR [Compatibility Mode]