EC2257 TRANSISTOR PHASE SHIFT OSCILLATOR Anna University lab manual - Computer Programming

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Monday, April 18, 2011

EC2257 TRANSISTOR PHASE SHIFT OSCILLATOR Anna University lab manual

TRANSISTOR PHASE SHIFT OSCILLATOR
AIM:
          To design and construct the transistor Phase shift oscillator.
APPARATUS REQUIRED:

S.NO
ITEM
RANGE
Q.TY
1
TRANSISTOR
BC 107
1
2
RESISTOR


3
CAPACITOR


4
CRO
( 0 – 30 ) MHz
1
5
RPS
(0-30) V
1
6
FUNCTION
GENERATOR
 (0-1 )MHz
1

CIRCUIT DIAGRAM:



MODEL GRAPH:



 




DESIGN:
Given  :  Vcc = 12V ,  fo = 1 KHz,C = 0.01µF; IE = 5mA.;  Stability factor = 10
                             f = 1/ 2πRC   Find R
                             R1 = (Ri – R)
                             R >> Rc
                             Βeta = -1 / 29              
Amplifier Design :
Gain formula is given by
                        Av = -hfe RLeff / hie ( Av = 29, design given )
Assume,         VCE = Vcc / 2
                   RLeff = R c | | RL
                   re = 26mV / IE
                                hie = β re where re is internal resistance of the   transistor.
                       hie = hfe re
                   VE = Vcc / 10
On applying KVL to output loop,
                   Vcc = IcRc + VCE + IERE
                   VE = IERE
                         Rc = ?
Since IB is very small when compared with Ic
                   Ic approximately equal to IE
                   RE = VE / IE = ?
                   VB = VBE + VE
                   VB = VCC . RB2 / RB1 + RB2
                             S = 1+ RB /  RE
                             RB =?
                             RB = RB1|| RB2
   Find RB1 & RB2
          Input Impedance, Zi = (RB || hie )
          Coupling and bypass capacitors can be thus found out.
          Input coupling capacitor is given by , Xci = Z i / 10
                             Xci = 1/ 2pf Ci
                             Ci = ?
          output coupling capacitor is given by ,
                             Xc0 = 1/ 2pf Co
                               Co =?
          By-pass capacitor is given by, XCE = 1/ 2pf CE
                             CE =?
          THEORY:
          The Transistor Phase Shift Oscillator produces a sine wave of desired designed frequency.  The RC combination will give a 60° phase shift totally three combination will give a 180° phase shift. . The BC107 is in the common emitter configuration.  Therefore that will give a 180° phase shift totally a 360° phase shift output is produced.  The capacitor value is designed in order to get the desired output frequency.  Initially the C and R are connected as a feedback with respect to input and output and this will maintain constant sine wave output. CRO is connected at the output.
PROCEDURE:
1.   The circuit is constructed as per the given circuit diagram.
2.   Switch on the power supply and observe the output on the CRO( sine wave)
3.   Note down the practical frequency and compare it with the theoretical frequency.
RESULT :

Theoritical
Practical
Frequency
f = 1 / 2 P RC Ö6RC 


4. LC OSCILLATOR – HARTLEY and COLPITT OSCILLATOR

AIM :
 To Design and construct the given Oscillator at the given
operating frequency.
APPARATUS REQUIRED:
S.NO
ITEM
RANGE
Q.TY
1
TRANSISTOR
BC 107
1
2
RESISTOR

1

3
CAPACITOR


4
CRO
(0 – 30)MHZ
1
5

RPS
(0-30) V
1
6
FUNCTION
GENERATOR
(0- 1 ) MHz
1
7
DlB, DRB

1
CIRCUIT DIAGRAM : 
                                     
                                                             
                                           



CIRCUIT DIAGRAM:

                                                                                             +VCC  







 

                                RB1                         RC
                                                                                          0 .01mF
                               Cin                         C                           
                                                       B
                                                                          BC107                                            
                                                                                                                                RL
Oval: CRO                                                                       E













 

                                                      RE            CE               
                                 RB2
























 



     C1               C2
                                                                                                                                 
                                  
 

                                                       L

MODEL GRAPH:
                        





 





Design of Feedback Network ( Hartely Oscillator ) :
Given : L1 = 1mH ; f = 800kHz; Vcc = 12V ; Av =50 ; fL = 1Khz
              Av = 1 / β = -L1 / L2
          F = 1/2π√(L1 + L2)C;         C = ?
Design of Feedback Network ( Colpitt Oscillator ) :

Given :      C1 = 0.1μF;f =800kHz; Vcc = 12V ; Av = 50 ; S = 10
                   IE = 5mA; fi = 1kHz
          Av = Av = 1 / β = C2 / C1
          f = 1/2π√(C1 + C2) / LC1C2
        L = ?
 Amplifier Design :
Gain formula is given by
                        Av = -hfe RLeff / hie ( Av = 29, design given )
Assume,         VCE = Vcc / 2
                   RLeff = R c | | RL
                   re = 26mV / IE
                                hie = β re where re is internal resistance of the   transistor.
                       hie = hfe re
                   VE = Vcc / 10
On applying KVL to output loop,
                   Vcc = IcRc + VCE + IERE
                   VE = IERE
                         Rc = ?;RL = ?
Since IB is very small when compared with Ic
                   Ic approximately equal to IE
                   RE = VE / IE = ?
                   VB = VBE + VE
                   VB = VCC . RB2 / RB1 + RB2
                             S = 1+ RB /  RE
                             RB =?
                             RB = RB1|| RB2
   Find RB1 & RB2
          Input Impedance, Zi = (RB || hie )
          Coupling and bypass capacitors can be thus found out.
          Input coupling capacitor is given by , Xci = Z i / 10
                             Xci = 1/ 2pf Ci
                             Ci = ?
          output coupling capacitor is given by ,
                             Xc0 = (Rc ׀׀RL) / 10
Xc0  = 1/ 2pf Co
                               Co =?
          By-pass capacitor is given by, XCE = RE / 10
XCE = 1/ 2pf CE
                             CE =?
THEORY:
 LC oscillator consisting of a tank circuit for generating sine wave of required frequency. Rectifying Barkhausen criteria Ab for a circuit containing reactance Ab must be positive and greater than or equal to unity.
PROCEDURE :
1. The circuit connection is made as per the circuit 
    diagram.
2. Switch on the power supply and observe the output 
    on the CRO(sine wave ).
                   3. Note down the practical frequency and compare it 
                  with the theoretical frequency.
THEORETICAL FREQUENCY FOR HARTLEY OSCILLATOR:
 

THEORETICAL FREQUENCY FOR COLPITT OSCILLATOR:
fc = 1/2π√(C1 + C2) / LC1C2



PRACTICAL :
Observed Values:
Time Period =
 Frequency  = 


RESULT :
          Thus the LC oscillator is designed for the given frequency and the output response is verified.
                  

Theoritical
Practical

Frequency
Hartley




Colpitt

Hartley
  Colpitt





                         

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