The Wien-bridge oscillator is widely used for generating sinusoids in the frequency range below 1 MHz . It is an RC op amp circuit which is easy to design and easily tuneable, shown in Fig. 1.
Figure 1
( v_{2} / v_{0} ) is the feedback ratio. To satisfy the second Barkhausen stability criterion, ( v_{0} ) and ( v_{2} ) must in the same phase, see detail in pp. 439-441. So that we have oscillation frequency
[
f_{0}=frac{1}{2 pi R C}
]
When in most practical applications ( R_{1}=R_{2}=R, C_{1}=C_{2}=C ), we have ( R_{f} geq 2 R_{g} ).
3.1 Show how equation ( R_{f}=2 R_{g} ) is arrived. (Based on ideal situation of Fig.1, Barkhausen stability criterion 1 and noninverting amplifier)
3.2 In the Wien-bridge oscillator circuit in Fig.1, let ( R_{1}=R_{2}=12.5 mathrm{~K} Omega, C_{1}=C_{2}=1 n F ). Determine the frequency ( f_{0} ).
Workings and Comments:
3.3 Base on the provided resistors and capacitors in required equipment, design a Wien-bridge oscillator around 1
KHz .
Workings and Comments:
