Design and simulation of tunable low-pass Gm-C filter with 1 GHz cutoff frequency based on CMOS inventers for high speed telecommunication applications

A tunable low-pass Gm-C filter with 1 GHz cutoff frequency is presented. The core of this filter is a high frequency low voltage operational transconductance amplifier (OTA) in which CMOS inverters are used. For enhancing the linearity of the filter, a novel common mode feedforward circuit is merged with a common mode feedback circuit. Moreover, in this paper, a new tuning circuit is presented for tuning transconductance in order to compensate effects of elements mismatch and temperature variations on OTA. Accordingly, the cutoff frequency is compensated by the bulk voltage tuning, while this circuit is less complex and consumes low power. The circuit is designed and simulated using TSMC 90 nm CMOS technology and a 1 V power supply. The results of simulation show that the DC differential gain, - 3 dB cutoff frequency and the unity-gain frequency of OTA are 37.7 dB, 325 MHz and 25 GHz, respectively. After applying two-tone input voltages 0.2 Vp-p, the IM3 value of the filter at 1 GHz is - 36 dB. The filter consumes 8 mW of power and occupies an area of 0.113 mm x 0.144 mm.