Fully differential current-mode third-order Butterworth VHF Gm-C filter in 0.18 μm CMOS

Abstract

The authors present a new fully differential current-mode third-order Butterworth very high frequency Gm-C filter using current-mode linear transformation (CMLT) techniques. The systematic design method and procedure are developed to realise CMLT Gm-C filters efficiently. A third-order Butterworth lowpass filter with 200 MHz cutoff frequency, embedded bandgap reference and bias circuit is implemented in a TSMC 0.18 μm 1P6M process. The total harmonic distortion of the proposed current-mode filter is −46.5 dB at 200 MHz with input signal 0.4 mA. Power dissipation is 16.77 mW under 1.8 V supply voltage. Its core area occupies 0.163×0.186 mm2. Both post-layout simulation and experimental results confirm the theoretical analysis. The proposed circuits can be extended to high-order Chebychev and elliptic filters.