Data Sheet AD8515
Rev. E | Page 15 of 16
WIEN BRIDGE OSCILLATOR
The circuit in Figure 38 can be used to generate a sine wave, one
of the most fundamental waveforms. Known as a Wien Bridge
oscillator, it has the advantage of requiring only one low power
amplifier. This is an important consideration, especially for battery-
operated applications where power consumption is a critical issue.
To keep the equations simple, the resistor and capacitor values
used are kept equal. For the oscillation to happen, two conditions
have to be met. First, there should be a zero phase shift from the
input to the output, which happens at the oscillation frequency of
Second, at this frequency, the ratio of VOUT to the voltage at the
positive input (+IN, Pin 3) has to be 3, which means that the
ratio of R11:R12 should be greater than 2.
03024-038
C10
1nF
C9
1nF
R19
1kΩ
VEE
VCC
R13
1kΩ
R12
1kΩ
1
AD8515
3
2
U10
V+
V–
+
–
R11
2.05kΩ
F
igure 38. Low Power Wien Bridge Oscillator
High frequency oscillators can be built with the AD8515,
due to its wide bandwidth. Using the values shown, an oscilla-
tion frequency of 130 kHz is created and is shown in Figure 39.
If R11 is too low, the oscillation might converge; if too large,
the oscillation diverges until the output clips (V
S
= ±2.5 V,
f
OSC
= 130 kHz).
03024-039
VOLTAGE (2V/DIV)
F
igure 39. Output of Wien Bridge Oscillator
