Design of a New Variable Gain Amplifier

This paper proposes a new variable gain amplifier (VGA) using the tunable exponential tail current source. Compared to the traditional digitally controlled VGA where constant tail current source is applied, the proposed design improves the dynamic range due to the larger current provided by the exponential tail current source. Moreover, tail current source array is used in this work to further increase the dynamic range. This new VGA circuit design is completed using SMIC $\mathbf{0.18}\ \mu\mathbf{m}$ CMOS process in Cadence. The simulation results show that the total exponential tail current for each stage ranges from $\mathbf{4.7}\ \mu \mathbf{A} -279\ \mu \mathbf{A}$, and a dynamic range of −3 dB ~35 dB, with 6.67 MHz bandwidth is achieved.