1
Sin –wave Oscillators
Loop gain and phase
+ =
= ()1 − ()
Oscillations – positive feedback
= ()1 − ()
1 = =
=1
+=n∙360°AMPLITUDE condition
PHASE condition (n=0,1,2..)
2
Phase and Amplitude conditions
=1 +=n∙360°usually |KV(U)β| > 1
U increases KV(U) decreases
so:
amplitude of oscillation is
limited
so:
frequency of oscillation is
adjusted
Wien-bridge oscilator
f – [Hz]
|β|=|Uout/Uin|
1/3
f – [Hz]
90o
-90o
fr
=1
2
Wien oscillator
=1
2
nonlinear
resistor =
!"
!""(#)+1≈ 3
3
Twin-T filter
f – [Hz]
|β|=|Uout/Uin|
1
f – [Hz]
90o
-90o
fr
=1
2
Wien oascillator– automatic gain control
Twin- T oscillator
!&!' =10⋯1000
4
Phase-Shift oscillators
=1
2 6
φβ=180o KV>30
Phase-Shift oscillators
=1
2 6
φβ=180o KV>30
LC oscillatorsresonant circuit (serial)
f – [log]
|Z/r|
1
f – [Hz]
90o
f0
-90o
45o
-45o
√2
>f
+ =1
2 ,
- = +∆ =
ω+,0
5
LC oscillatorsresonant circuit (serial)
f – [log]
|Z/R|
1
f – [Hz]
90o
f0
-90o
45o
-45o
√2
>f
+ =1
2 ,
- = +∆ =
ω+
Meissner (Armstrong) oscillator
+ =1
2 ,
(+) =121
3 =1 12βKV
z1:z2
MIESSNER
+ =1
2 ,
(+) =121
3 =1 12
6
+ =1
2 (,2+, )
(+) =, ,2
3 =,2,
Hartley oscillator
Hartley oscillator
+ =1
2 (,2+, )
(+) =, ,2
3 =,2,
Colpitts oscillator
+ =1
2 , 2 2 +
(+) =2
3 = 2
7
Colpitts oscillator
+ =1
2 , 2 2 +
(+) =2
3 = 2
Colpitts oscillator
CE
CE, CC, CB amps in oscillators
CE CB CC
8
FET amps as oscilltorsCG, CD, CS
CG CD CS
Clap oscillator
+ =1
2 ,
(+) =2
3 = 2
24 =
24'+
24&+
245
Quartz (crystal) oscillatorClap
9
Crystal equivalent circuit
4.06 4.07 4.08 4.09 4.1 4.11 4.12 4.13 4.14x 106
102
103
104
105
Q=25e3
|Z|[Ω]
|Z(f)|
106
1070
1
2
3
4
5
6
7
8x 104
|Z|[Ω]
Series and Parallel resonance
4.06 4.07 4.08 4.09 4.1 4.11 4.12 4.13 4.14x 106
102
103
104
105
6 =1
2 , 7 =1
2 , 8+8 + +
|Z|[Ω]
- = 25000
10
-E
+ER1
R2
R3
UWY
X
-E
+E
R1 R2
R3
UWY
X
fs - |z|=minfp - |z|=max
series resonans
Pirce oscillator – an example
11
Frequency stability
Type of oscillator Stability
RC 10e-2 - 10e-3
LC 10e-3 - 10e-4
Crystal 10e-6 - 10e-7
Crystal (temp. stab.) (10e-8 - 10e-10)
Atomic references 10e-12 - 10e-14
+(:) = 0± ∆0< =
∆00 24ℎ?
Features of oscillators
• frequency stability
• harmonics (THD)
• frequency range
• amplitude and phase noise
Summary
• amplitude and phase conditions of oscillation
• Wien bridge generator
• Twin – T filter and oscillator
• RC phase shifter oscillators
• Meissner, Hartley, Colpits oscillators -topologies
• crystal (quartz) - parallel and series resonances
• frequency stability and other parameters of generators
12
Flip-Flopsand multivibrators
BJ-Transistor as a switch
Uin
Uout0.6-1V
0.1-1V
Vcc
UH
UH
UL
UL
MH
ML
MOSFE-Transistor as a switch
Uin
Uout0.6-3V (UTH)
0.01-1V
Vcc
UH
UH
UL
UL
MH
ML
13
Dynamic feathuresdelay-, fall-, storage-, rise-time
Uout
t
UH
UH
UL
ULtd
ML
Uin
t
tf
tstr
100%90%
10%
Dynamic feathurespropagation delay time
Uout
t
½(UH+UL)
tpdHL
Uin
t
tpdLH
100%
50%
RS flip-flop
T1 T2
RC
+VCC
RC
R1R2
RS RR
S R
14
Astable Flip-Flop
4 ≪ 2, ≪ 4:2 ≈ 0.722 : ≈ 0.7
Astable Flip-Flop with NAND Gate
221121
11
CRCRttf
+=
+=
OpAmp(Comparator) Flip-Flop
ββ
−+=
1
1ln2 1CRT
32
3
RR
R
+=β
15
Timer „555” – monostable discipline
RCT ⋅= 3ln
Timer „555” – astable discipline
(2/3)VCC
(1/3)VCC
( )CRRTf
BA 2)2ln(11+
==
BA
BA
RRRR
Tt
D2
1
++==
VCO F-F- Emmiter coupling
CUI
fBE4
=
16
Emitter coupled
Voltage-controlled multivibrator
MC4024
Sine, Triangle, Square generator
Układ kształtujący
Sine, Triangle, Square generator -IC
17
Sine, Triangle, Square generator -IC
ICL8038obsolet
Sine, Triangle, Square generator -IC
DDS - Direct Digital Synthesis
18
Summary
• Flip-Flop as a- and mono-stable
• Timer 555
• Function generator
