New Monolithic Switched-Capacitor Differentiators with Good Noise Rejection

Inverting and noninverting switched-capacitor (SC) differentiators suitable for integrated-circuit implementation are proposed and analyzed. Their structures are simple, parasitic-free, and less sensitive to offset voltage and power-supply voltage changes. In addition, their fabrication process and operating clocks are fully compatible with conventional SC integrators. Noise analysis on the SC differentiators shows a good low-frequency noise-rejection capability. Moreover, the high-frequency noise can be suppressed and does not over-drive the output of the SC differentiators. To demonstrate the application of the SC differentiators in the SC filter (SCF), a bandpass differentiator-type biquad is presented. Both differentiators and biquad were fabricated and measured. The measured differentiation waveforms and the good consistency between the measured and the SWITCAP simulated circuit responses verify the correct operation of the SC differentiators. As a complementary circuit to integrators, the SC differentiators make feasible many interesting new applications and provide different features for the SC circuits.