Op Amps for Everyone - The Repeater Builder's Technical ...

Sine Wave Oscillator Circuits
C 1
0.1 µF
+
−
V C1
R 2
11.3 kΩ
R 1 10 kΩ
R G2 10 kΩ
V D1
+ −
D1 1N4933
R F 18.2 kΩ
_
J1
+
V OUT
−
R S
10 kΩ
+
R G1
10 kΩ
C
R
R
C
V REF = 2.5 V
Figure 15–12.
Wien Bridge Oscillator with AGC
V OUT = 1 V/div
Time = 500 µs/div
Figure 15–13. Output of the Circuit in Figure 15–12
15.7.2 Phase Shift Oscillator, Single Amplifier
Phase shift oscillators have less distortion than the Wien bridge oscillator, coupled with
good frequency stability. A phase shift oscillator can be built with one op amp as shown
in figure 15–14. Three RC sections are cascaded to get the steep dφ/dω slope as described
in Section 15–3 to get a stable oscillation frequency. Any less and the oscillation
frequency is high and interferes with the op amp BW limitations.
15-14