chapter 4 oscillthere are many types of voltage regulator. in this assignment, we need to design an...

7/26/2019 Chapter 4 OscillThere are many types of voltage regulator. In this assignment, we need to design an adjustable voltage regulator that can adjust voltage from 5V to 12V. First,

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CHAE 4: CIA


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INTRODUCTION TO OSCILLATORAn oscillator is a circuit that produce a periodic waveform on its output with

only the dc supply voltage as an input.

Converts electrical energy from dc power supply to periodic waveforms.

DC

: , . F


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OSCILLATORC :

: G

: , , .

.

, .

: I


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OSCILLATOR: SQUARE WAVEConsist of three types:

- Astable: neither state is stable ; continues square wave form.

Application: Oscillator.

A

-Monostable : One of the state stable and another one is not.

Application: Timer

: I E


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OSCILLATOR: SQUARE WAVE-Bistable: Two stable state.

-Application: flip-flop

B


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SQUARE WAVE OSCILLATOR:OPERATIONAL AMPLIFIER (ASTABLE)

.

V

2 3, =

+

V +V


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: ' .

= = 0 , >

=


V +V V+

)(satoV CCV+

.

A , :

+)(satoV 11CR=

+)(satoV

( ) )(32

3)(0

32

3CCsatUTPf V

RR

RV

RR

RVVV +

+=

+=== ++

+V


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= =

( )

>

SQUARE WAVE OSCILLATOR:OPERATIONAL AMPLIFIER (ASTABLE)+

)(satoV CCV++V

V

V +V

=

C, C

. A

:

( ) )(32

3)(0

32

3CCsatLTPf V

RR

RV

RR

RVVV

+=

+=== +

)(sato

CR1=

)(satoV

+V


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SQUARE WAVE OSCILLATOR:OPERATIONAL AMPLIFIER (ASTABLE) .

: , H : HIGH .

:


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V

I E C ,

C

E

E+

V

I E = +CC

=

C

o

EE

EERCt ln

=

UTPCC

LTPCC

H VV

VVCRT ln

1

=

LTPCC

UTPCCL

VV

VVCRT ln1

LH

oTTT

f+

== 11


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SQUARE WAVE OSCILLATOR:OPERATIONAL AMPLIFIER (ASTABLE)E 1: B , ,

,


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SQUARE WAVE OSCILLATOR: TIMER555 (ASTABLE)

A 8 (IC).

A IC. .

A

IC.

.


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SQUARE WAVE OSCILLATOR: TIMER555 (ASTABLE) : +5 +18.

1,2,3

.

D CC

.

, :

: 5

( )

CCCBR

CCCARR

VVV

VVV

3

1

3

2

3

32

==

==

+

+


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SQUARE WAVE OSCILLATOR: TIMER555 (ASTABLE) C A B :

.

C A

( 6) > ,

CAHIGH.

( 6) <

CAV +

CCCA VV

3

2

CAV +

CCCA VV 2

CA.

C B

( 2) > ,

CA.

( 2) <

CAHIGH

CBV

+CCCB VV

3

1

CBV

+CCCB VV

3

1


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SQUARE WAVE OSCILLATOR: TIMER555 (ASTABLE) F:

Q

HIGH HIGH HIGH HIGH

HIGH HIGH I


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SQUARE WAVE OSCILLATOR: TIMER555 (ASTABLE) I: .

( 4): 555

.

(1) & (2)


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SQUARE WAVE OSCILLATOR: TIMER555 (ASTABLE)1. C C1

2(IGGE ) 6(EHD ).

2. C1

.

CCV3

2

CCV3

1

3. A, B C1 ()

.

4. C2

( 5)

2 3.5. C2

555

.


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SQUARE WAVE OSCILLATOR: TIMER 555 (ASTABLE)B 0:

C1 .

2= 6=0.

CBHIGH

2(0) < 3( )

CA

CCV3

1

(2+3)( )> 6(0)

FF ,

1 .

H .

C

A B +

CCV

3

Q


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SQUARE WAVE OSCILLATOR: TIMER 555 (ASTABLE) 0 1:

C1(2)

CB

2( ) > 3( )

CA

CCV3

1

CCV3

1

CCV3

1

(2+3)( )> 6( )

FF ,

1 FF.

H .

CCV

3

Q

CCV

3


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SQUARE WAVE OSCILLATOR: TIMER 555 (ASTABLE) 1 2:

C1(2)

CB 2( ) > 3( )

CAHIGH

+ <

CCV3

1

CCV3

2

CCV3

2

FF , HIGH

1 .

.

C C1

0 B

1

CCV

3Q

CCV

3


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SQUARE WAVE OSCILLATOR: TIMER 555 (ASTABLE) 2 3: C1

CBHIGH 2( ) < 3( )

CA

+ > 2

CCV3

1

CCV3

1

CCV3

1

1

FF ,

1 FF.

HIGH .

C C1 +

A B. ,

.

3

Q

CC3

CCV3

2


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SQUARE WAVE OSCILLATOR: TIMER 555 (ASTABLE)

2 ( )

6 ( )


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C C1 +

A B. HIGH :


CCV3

2CCV

3

1

( ) 11

693.02ln

3

21

3

1

1ln

3

23

1

ln

CCT

CRR

VV

VVT BA

CCCC

CCCC

H

+=+=

+=

=

C11


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C C1 +

B. :

SQUARE WAVE OSCILLATOR: TIMER 555 (ASTABLE)CCV

3

2CCV

3

1

( ) ( )11

693.0

2ln

3

10

3

20

ln

CRT

CR

V

V

T B

CC

CC

L

=

=

=

C12


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:


1

11

)2(693.0

)(693.0)(693.0

CRRT

CRCRRT

TTT

BA

BBA

LH

+=

++=

+=

D C:

T

%1002

%100

)2(693.0

)(693.0

%100

1

1

+

+=

+

+=

+=

=

BA

BA

BA

BA

LH

H

RR

RRD

CRR

CRRD

TT

TD

T


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E 1: F ,0, D , D ,

.



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SQUARE WAVE OSCILLATOR: TIMER555 (MONOSTABLE)1. , .

2. 6 () 7(D)

C.

3.

.

4. 4() +, 2

.

5. 5 (C )

2 3.


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B 1:

CB 2(+)> 3( )

CA

2+3 > 6 0

SQUARE WAVE OSCILLATOR: TIMER555 (MONOSTABLE)

2

CCV3

1

FF , HIGH

1 .

.

3

Q


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1 2:

CBHIGH 2(0) 6


2

CCV3

1

FF ,

1 FF.

C C + .

HIGH.

3

Q


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2 3:

CB

2(+)>3( )

CA

2+3 > 6


2

CCV3

1

FF ,

1 FF.

C C + .

3

Q


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A 3:

CB

2

(+)>3( )

CAHIGH

2+3 > 6


2

CCV3

1

2

FF , HIGH

1

C C 1 0.

3

Q

3


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C 0

SQUARE WAVE OSCILLATOR: TIMER 555 (MONOSTABLE)

CCV3

2

RCRCRC

VV

VRCPW

CCCC

CC

1.1)3ln(2

01ln

3

2

0ln

==

=

=

3


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D :

, C .

I()

, I .

I 555 .

CCV3

1

I() I()=1000 I.

I() = = . ,

,CCV

3

2

(min)

(min)

3

3

1

C

CC

CC

Rc

I

VR

R

V

RVI

=

==


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Example 2:

Design a monostable circuit by using timer 555 with following specification:

Pulse width, PW =1s.

Voltage Source, +Vcc=+15 V

Given threshold current, Ith = 0.25s


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OSCILLATOR: SINUSOIDAL WAVECONCEPT OF OSCILLATOR: POSITIVE FEEDBACK OSCILLATOR

*Positive feedback: a portion of amplifier output is fed back to the

input with no net phase, resulting a reinforcement output feedback.

(a)The loop is created in which the signal sustains itself and a

continuous sinusoidal output produced. (Oscillation phenomena)

(b) Some types of amplifiers, the feedback circuit shifts the phase180 and an inverting amplifier is required to provide another 180

phase shift so there's no net phase shift.

* C .


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OSCILLATOR: SINUSOIDAL WAVECONDITION FOR OSCILLATION

Two condition for oscillation circuit:(a)The phase shift around feedback loop must be effectively 0.

(b) The voltage gain, Acl around the closed feedback loop (loop gain)must equal 1(unity).


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OSCILLATOR: SINUSOIDAL WAVESTART UP CONDITION:

A small positive feedback voltage develops from thermally produced

broad-band noise in the resistor or other components or from power

supply turn-on transients.


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OSCILLATOR: THE WEIN-BRIDGE OSCILLATORWein-bridge oscillator using a lead-lag feedback circuit.

1

2 12

AA

CC C C


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OSCILLATOR: THE WEIN-BRIDGE OSCILLATORWein-bridge oscillator using a lead-lag feedback circuit.

1. R1 and C1 form lag portion.

2. R2 and C2 form lead portion.

3. At lower frequency, lead circuit dominant due to high reactance of C2.

4. As frequency increase, XC2 decrease, thus allowing the Vout to increase.5. As the frequency increase and reach the resonant frequency, or oscillation frequency,

f0, Vout increase and reach maximum value.

6. After that, lag portion will take over and become dominant circuit and decreasing value

.


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OSCILLATOR: THE WEIN-BRIDGE OSCILLATORAt the response curve:1. Output voltage peaks at a frequency called the resonant frequency, fr. (Phase shift=0)

2. At this point, the attenuation of the circuit, (Vout/Vin) is 1/3, if R1 = R2 and XC1=XC2 .

== 3

1

in

out

V

V

RCfr 2

1

=

Lead dominates Lag dominates


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OSCILLATOR: THE WEIN-BRIDGE OSCILLATORCONDITION TO OSCILLATE:

1

2

CC

3

13

1

1

=

=

=

==

A

AA

AA

cl

cl

A

21

2

1

2

1

2

12

2

2

13

1

RR

R

R

R

R

RRRA

=

=

+=

+== Initially, the amplifier gain, A itself must be

more than 3 (A>3) in order to start the

oscillation until output voltage,V0 reach the

needed voltage and then decrease to

maintain amplifier gain, A=3


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OSCILLATOR: THE WEIN-BRIDGE OSCILLATORMETHOD IN ARCHEIVING SUSTAIN OSCILLATION:

1. Voltage divider circuit has been modified by including additional resistor R3 in parallel

with back to back zener diode.

2. When DC source apply, both zener diode appear as open. During this period,

amplifier gain:

2

3210

R

RRR

V

VA

f

++==

since R1=2R2

2

3

2

32

2

322

3

32

R

RA

R

RR

R

RRRA

+=

+=

++=


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1. Initially, a small positive feedback signal develops from noise or turn on transients.

2. The lead-lag circuit permits only a signal with frequency equal to fr to appear in

phase on the noninverting input.

3. This feedback signal is continuously amplified resulting a build up output voltage.4. When the output signal reaches zener diode breakdown voltage, the zeners conduct

and short out R3. This lowers the amplifier gain to 3.

5. Thus loop gain equal to 1 and oscillation is sustained.


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Example 3: Based on figure below;

a. Determine the resonant frequency, fr .

b. Analyze whether the amplifier circuit able to generate oscillation or not.

Given value R=1.5k and capacitor value C=0.1F.


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OSCILLATOR: THE COLPITTS OSCILLATOR

1. Uses an LC circuit in the feedback loop to provide the necessary phase shift and to

act as a resonant filter that passes only the desired frequency oscillation.

2. Resonant frequency, fr,

,2

1

LCf

T

r

21

21

CCCCCT+

=


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OSCILLATOR: THE COLPITTS OSCILLATORCONDITION FOR OSCILLATION AND START-UP:

1. The feedback gain, ,depends on value C1 and C2.

2. Oscillation happens when; 1

2

C

C=

2 1

1

CAA

AA

cl

cl

=

=

==

3. For oscillator to be self starting, A > 1. Therefore the voltage gain must be made

slightly greater than C1/C2. After that, A will be decrease to A =1 to maintain V0

amplitude.

2

1

1

C

CA=

2

1

C

CA>


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Loading of feedback circuit affects the frequency of oscillation:

1. Based on Figure 3, the input impedance of the amplifier acts as a load on the

resonant feedback circuit and reduce the Q of the circuit.

2. The resonant frequency depends on the Q:

12

2

= Q

frZin Vout

3. Rule of thumb:

Q > 10;

Q


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Example 4: Based on figure below;

a. Find the resonant frequency, fr.

b. Amplifier gain,A.

Ignore the load at positive feedback network and given quality factor,Q = 15.

chapter 4 oscillthere are many types of voltage regulator. in this assignment, we need to design an...

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