Feed forward third order switched capacitor filter for different circuit merit factor Q values

By G. N. Shinde, S. R. Bhagat


This paper proposes feed forward third order switched-capacitor filter. The circuit consists of only op-amps and switched capacitors. The circuit is designed for cut-off frequency 20 kHz. The proposed circuit implements three filter functions low pass, band pass and high pass simultaneously in single circuit. The circuit characteristics are studied for various values of circuit merit factors. In band pass operation pass band gain increases with increase in the value of Q. However pass band gain remains almost same for low pass filter. The gain-roll off for this circuit is close to the ideal value of 60dB as for third order filters. Thus, the circuit shows better response for Q > 10 and f0 =20 kHz.


Key Words : Feed forward, third order filters, Switched capacitor (SC), pass band gain, Circuit merit factor, gain roll-off.


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