A highly linear low-passG_m–Cfilter with a self-biasing transconductor for a digital TV tuner

Abstract

A technique of multiple gated transistors on the basis of self-biasing circuit in this paper is chosen to enhance the linearity of the transconductor, whereas decreasing the bill-of-material (BOM) and complexity of the design. The transconductor is chosen by third-order chebyshev which tracks low-pass filter with low power consumption. The filter cutoff frequency is 50-200 MHz. The hybrid tracking low-pass filter is designed to defeat the problems related to a local oscillator harmonic-mixing for Advanced Television System Committee terrestrial digital TV tuner integrated circuit. The proposed operational transconductor amplifier (OTA) is designed in 90 nm CMOS technology. The simulation result with two-tone test at 100 MHz center frequency shows that the proposed OTA has 5 dBm Input-referred Third-Order Intercept Point (IIP3) improvement compared with a single-gate OTA in the third-order Chebyshev filter. The proposed OTA achieves maximum noise figure (NF) of 13 dB and maximum IIP3 of approximately 21.7 dBm at 100 MHz, whereas consuming 18 mA with 1.2 V supply voltage.