Lecture - 20: Applications of Operational Amplifiers
 

As triangular voltage increases the voltage v1 also increases. At t = T1, when the voltage vout becomes Vmax, the voltage v1 becomes equal to VR and switching takes place. Therefore,


Similarly, when output voltage is +Vsat, the voltage v1 is given by

As triangular voltage decreases the voltage v1 also decreases. At t = T2, when the voltage vout becomes Vmin, the voltage v1 becomes equal to VR and switching takes place. Therefore,


Therefore,

Solving the above equations, we get

The frequency f is independent of VO, maximum frequency is limited either by slew rate or its maximum output current which determines the charging rate of C. Slowest speed is limited by the bias current of OPAMP.

If unequal sweep intervals T1≠ T2 are desired, then VS can be changed. The positive sweep speed is given by (Vsat + VS) / RC and the negative sweep speed is given by (Vsat -VS)/ RC. The peak-to-peak triangular amplitude is unaffected by the voltage VS.


Therefore,

Similarly, when the output voltage of first OPAMP is –Vsat, then

Therfore,

Therefore,

The oscillation frequency is given by

and the duty cycle is given by

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