AD8515

Rev. D | 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

C10

R10

f

OSC

×

π

=

2

1

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.

C10

1nF

C9

1nF

R19

1kΩ

VEE

VCC

R13

1kΩ

R12

1kΩ

1

AD8515

3

2

U10

V+

V–

+

–

R11

2.05kΩ

Figure 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,

Figure 39. Output of Wien Bridge Oscillator