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

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## Monday, April 18, 2011

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
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