It contains an inverting amplifier, and a feedback network which 'shifts' the phase of the amplifier output by 180 degrees at the oscillation frequency.

It consists of:

An Amplifier with gain K

Three section RC network in feedback.

The circuit oscillate at the frequency for which RC Phase shift is 180

Phase Shift Oscillator

although two cascaded RC sections eventually provide 180 phase shift, the value of d/d at the oscillator frequency is unacceptably small.

oscillators made with two cascaded RC sections have poor frequency stability. Three equal cascaded RC sections have a much higher d/d and the resulting oscillator has improved frequency stability

The RC phase shift oscillator

Total loop phase shift=180o-180o=0o

The frequency can be varied by varying R or C values in the phase shift network.

Feedback n/w

phase shift= 60o *3=180o

Gain N/W phase shift= -180o

The RC phase shift oscillator

( )( )

RR

A

RCf

RC

RC

RCwhere

jVV

f

o

o

o

o

f

===

=

=

=

====

=

291291

6216

1

616

06

1:

)6(511

22

2

2

3

32

Total loop phase shift=180o-180o=0o

The frequency can be varied by varying R or C values in the phase shift network.

Feedback n/w

phase shift= 60o *3=180o

Gain N/W phase shift= -180o

A Phase shift Oscillator with a limiter for amplitude stabilization.

The op-amp RC oscillators are normally useful for operation in the range of 10 Hz to 100 kHz.

High-frequency oscillations in the range of 100 kHz to hundreds of MHz are obtained using LC or crystal oscillators.

LC Oscillators

)()(

))((

||:

312321

21

31

1

31

1

3120

ZZZZZZRZZAA

ZZZRZZAA

ZZZ

ZZZZwhereZR

ZAVVA

o

v

Lo

Lv

LLo

Lv

f

++++=++

=+=

+=+==

12

2

1

2112

21

213321

312321

21

332211

1)(

)(0)()(

,,

XXA

XXA

XXXXXXAA

XXXXXXXXXXXXjR

XXAA

jXZjXZjXZ

v

vv

o

v

=

===+==++

+++====

21

21

2121

32

21

1

1

2

2121

32211

&2

1,011

,&1,1:

&)(2

1,01

1&,:

CCA

CCCCL

fLCC

LXC

XC

XOscilatorColpits

LLA

CLLf

CLL

CXLXLXOscilatorHartley

vo

vo

=+

==+

===

=+==+

===

I

FV R

RA =

CMOS Ring Oscillator.

Cascade connection of identical inverters (Odd Number)

f = 1/(2.n.p)

The idea of the quadrature oscillator is to use the fact that the double integral of a sine wave is a negative sine wave of the same frequency and phase, in other words, the original sine wave 180deg phase shifted.

The phase of the second integrator is then inverted and applied as positive feedback to induce oscillation

quadrature oscillator

A quadrature oscillator is a circuit that generates two periodic signals that are in quadrature, i.e., they are 90 degrees out of phase.

Inverting integrator with a limiter

tV= (1/C) (vo1/2R) dt

0

tvo2 = 2v = (1/C)(vo1/R) dt

0Non inverting integrator

For Rf = 2R