"Chapter 1 - The Op Amp's Place in the World" - HTL Wien 10

Sine Wave Oscillator Circuits
15-18
C
RG
360 kΩ
10 nF
R
10 kΩ
2.5 V
Figure 15–18. Bubba Oscillator
RF
1.5 MΩ
+5 V
_
+
+
_
4/4 TLV2474
C
R
10 kΩ
10 nF
R
10 kΩ
C
+
_
+
_
R
10 kΩ
10 nF C 10 nF
Time = 500 µs/div
Figure 15–19. Output of the Circuit in Figure 15–18.
VOUT = 1 V/div
VOUT
Sine
VOUT
Cosine
The gain, A, must equal 4 for oscillation to occur. The test circuit oscillated at 1.76 kHz
rather than the ideal frequency of 1.72 kHz when the gain was 4.17 rather than the ideal
gain 4. The output waveform is shown in Figure 15–19. Distortion is 1% for V OUTSINE and
0.1% for V OUTCOSINE. With low gain, A, and low bias current op amps, the gain setting