Design techniques for VHF/UHF high-Q tunable bandpass filters using simple CMOS inverter-based transresistance amplifiers

Abstract

In this paper, CMOS inverter-based wideband transresistance R(m) amplifiers are proposed and analyzed. Using the R(m) amplifiers, tunable VHF/UHF R(m)-C bandpass biquadratic filters can be designed. In these filters, the center frequency f(o) can be post-tuned by adjusting the control voltages of the R(m) amplifiers. The pseudodifferential configuration uses the extra inversely connected and self-shorted inverters for Q enhancement. Experimental results have shown that the center frequency f(o) of the single-ended-output R(m)-C bandpass biquad is 386 MHz (258 MHz) and Q = 1.195 (Q = 1.012) for +/-2.5 V (+/-1.5 V) supply voltage. The power consumption is 24.83 mW (3.42 mW), and the dynamic range is 61 dB (55.5 dB). For pseudodifferential-output high-Q configuration, the measured quality factor Q can be as high as 360 with f, = 222.7 MHz. When Q = 94, the power consumption is 56.2 mW and the measured dynamic range is 57.8 dB for +/-2.5 V supply voltage.