# Solved Problems-10

Problems-10

For the Notch-filter (Twin-T) network, determine:

*y*-parameters,- the voltage ratio transfer function
*V*_{2}/*V*_{1}when no-load impedance is present, and - the value of the frequency at which the output voltage is zero.

Solution

- The given network is the parallel combination of the two networks:

**(a) Network (b) Network**

For network (a),

âˆ´

âˆ´

For network (b),

âˆ´

âˆ´

Thus, the overall

*y*-parameters are,*y*

_{11}=

and

*y*_{12}=- Now,

When no-load impedance is present,

*I*_{2}= 0,âˆ´

- For
*V*_{2}= 0 â‡’ 1 +*R*^{2}*C*^{2}*s*^{2}= 0

Putting

*s*=*jÏ‰*, 1 â€“*Ï‰*^{2}*R*^{2}*C*^{2}= 0âˆ´

*Ï‰*=Thus, the notch frequency is given by,

*f*=_{N}