New CMOS Digitally Controlled Variable Gain Amplifier

A novel current-mode CMOS digitally controlled variable gain amplifier (VGA) is presented in this paper. The proposed VGA is based on new +/- 0.75V digitally programmable second-generation current conveyors (DPCCII) with digital current gain control. The input stage of the DPCCII is realized using two complementary MOS differential pairs connected in parallel to ensure rail-to-rail operation. The output stage consists of a class-AB push-pull circuit, which guarantees high current driving capability. The digital control of the DPCCII, based on transistor arrays and MOS switches, provides variable current gain using an n-bits code-word. All proposed circuits are simulated using PSPICE with CMOS TSMC 0.25 mu m technology.