On the use of Nauta's transconductor in low-frequency CMOS g(m)-C bandpass filters

This paper discusses the use of a transconductor, first proposed by Nauta for high frequency applications, in low frequency CMOS g(m) - C bandpass filters. The behavior of the transconductor is examined in detail, showing that the robust implementation of higher-order low-voltage filters is possible for center frequencies in the lower megahertz region. The experimental results are presented of the realization of two prototypes, a 0.6-mum CMOS 18th-order real bandpass filter and a 0.35-mum CMOS 7th-order complex (14th-order bandpass) filter, both with a center frequency of 3 MHz and a passband of 1 MHz. These filters comply with the specifications for the channel-select stage of the Bluetooth short-range radio receiver.