A miniaturized 35 GHz 65-nm CMOS digital-controlled differential variable gain amplifier

This paper presents a 35 GHz differential variable gain amplifier (VGA) with 4-bit digital-controlled gain-tuning using 65-nm CMOS process. Using the proposed miniaturized differential matching inductors, a core size of the VGA is only 0.53 (Formula presented.) 0.26 mm. The digital gain control mechanism is achieved using the digital version current steering topology. The measured gain control range of the VGA is from 17.4 to 9 dB at 35 GHz with 16 different linear-in-dB gain states. Thus, this work achieves the maximum peak gain per unit core size and maintains a much better gain control range per unit core size. The measured root mean square gain error is <0.29 dB and phase error is < (Formula presented.) from 34 to 36.5 GHz.