A 2 MHZ ANALOG ACTIVE RC LOW-PASS FILTER DESIGN

Abstract

A fifth-order Chebyshev analog low-pass filter with a cut-off frequency of 2 MHz and a pass-band ripple of 1 dB is implemented on a 0.8 um CMOS double-poly-double-metal process. The active filter is a cascade of a first-order integrator and two biquadratic sections. Each biquad is realized based on the Åkerberg-Mossberg structure which is independent of the gain-bandwidth of the amplifier. This approach is insensitive to high frequency parasitic effects of the amplifier and thus allows the filter to operate at megahertz range of frequencies. The major building block of the filter, the Class AB amplifier, has an efficient quiescent current control for effective power management. Additional circuitry such as switches and an AD converter are integrated for tunability of the filter cut-off frequency. Also integrated on-chip is an external resistor-based bias generator which provides accurate bias to all internal circuits. Power dissipation of the filter at 5 V supply measures 80 mW. The total die area is 7.8 mm2.