Biquadratic transconductance switched-capacitor filters

A new type of sampled data filter consisting of transconductance elements, switches and capacitors, and called a transconductor switched-capacitor (TSC) filter is presented. Transconductance elements do not degrade their performance within a wide frequency range and tunable ones are available. The synthesis of TSC filters is explained on the basis of a signal flow graph realizing the general z-domain biquadratic transfer function. The transconductance elements employed as active devices are readily available in various technologies and are easily implemented and more suitable than operational amplifiers in a CMOS technology. Because the building blocks are not involved in any continuous feedback, frequency compensation is not necessary for stability purposes. The filter coefficients are determined by the clock pulse width and the transconductances, both of which can be tuned, and the integrator capacitors. This method can be easily generalized to the higher order filters.<
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