DIGITALLY CONTROLLED CMOS BALANCED OUTPUT TRANSCONDUCTOR AND APPLICATION TO VARIABLE GAIN AMPLIFIER AND GM-C FILTER ON FIELD PROGRAMMABLE ANALOG ARRAY

A digitally controlled balanced output transconductor (DCBOTA) is proposed and analyzed. The proposed DCBOTA is based on the BOTA given in Ref. 1 and MOS switches. The DCBOTA transconductance is tunable in a range of 2n-1 times using n bits control word. The proposed DCBOTA is simulated using CMOS 0.35 μm technology and the results have shown the feasibility of the proposed DCBOTA. The simulation results show that the DCBOTA has a transconductance tuning range from 20 μA/V to 140 μA/V using 3 bits control word and a 3-dB bandwidth larger than 80 MHz. A general configurable analog block (CAB) based on the proposed DCBOTA, capacitor array and MOS switches, is also presented. A collection of the CABs, fully differential buffers (FDBUFs), and their interconnection to construct a field programmable analog array (FPAA) is introduced. The DCBOTA is also used to realize a wide band digitally controlled variable gain amplifier (DCVGA) and six-order lowpass filter with variable gain and tunable cutoff frequency from 1 MHz to 7 MHz.