A 71 dB 150 μW Variable-Gain Amplifier in 0.18 μm CMOS Technology

This letter presents a simple approach for ultra-lowpower and high-frequency variable gain amplifier (VGA) design, which requires no additional circuitry to generate the exponentiallike function. Thus, the power consumption and chip area of the designed VGA can be drastically reduced without deterioration of other performance. The inverse exponential-like dB-linear characteristic is achieved by utilizing a pair of complementary transistors as the load. The p-MOS transistor is self-biased in the saturation region, while the n-MOS transistor is biased in the sub-threshold region. To prove the concept, a five-cell VGA is fabricated in a standard 0.18 mu m CMOS technology. The measurements show that the power consumption of the VGA is less than 150 mu W and achieves a total gain range of 71 dB, out of which 45 dB is dB-linear with less than 1 dB gain error, as well as bandwidth of more than 50 MHz. The output P (1 dB) is better than 0 dBm and the minimum input-referred noise is 7.5 nV/root Hz.