A 5 GHz band CMOS low noise amplifier with a 2.5 dB noise figure

The noise performance of a radio receiver is largely determined by the noise figure of the first-stage amplifier. The amplifier also must have high gain and remain linear when presented with large input signals to minimize distortion in the receiver output. Amplifiers having high performance in the 5 GHz band are often composed of discrete components or integrated using GaAs or Si bipolar technologies. This work demonstrates a fully integrated high performance 5.25 GHz LNA realized with a 0.25 /spl mu/m linear CMOS technology.

1. Circuit Design

The circuit is a differential design composed of a pair of single-stage cascode amplifiers using n-channel MOSFETs (Figure 1.) The input devices are , and are connected in a common-source configuration. 0.41-nH inductors are used for source degeneration to increase linearity. The input signal is applied to the gates through 2.5-nH inductors which, with the source inductors, form the input match. The cascode configuration is used to reduce the high frequency roll off of the input devices due to the Miller effect. [2] The cascode devices are . The drains connect to the 3-V power supply via 3.3-nH inductors. These inductors, along with the on-chip 0.17-pF output capacitors, form the output match. An on-chip current source with an off-chip variable resistor generates bias voltage for the input MOSFETs. Connecting the gates directly to the power supply biases the cascode devices. Figure 1. Simplified Schematic of LNA