A compact biquadratic gm-C filter structure for low-voltage and high frequency applications

A compact new biquadratic g_m-C structure is developed to design low voltage, low power, and high frequency continuous-time filters. This architecture is proper for modern deep sub-micron CMOS processes with limited supply voltage. Also, a proper Q-enhancement technique is introduced which makes the implementation of high-Q stages feasible. One of the advantages of this technique is its independent tuning of frequency and Q. The simple architecture of the proposed biquadratic filter makes it useful for high frequency applications with proper dynamic range. Based on the new biquadratic architecture, a single 1.8 V supply, lowpass, sixth-order elliptic filter in a 0.18 μm CMOS process is realized. The cutoff frequency of this filter is 33 MHz and has a THD of -40 dB for a 0.2 Vpp, 8 MHz signal with an OIP3 of 4 Vpp. The filter consumes 1.2 mA and has 1.1 mV_rms total noise.