A gain stabilization technique for tuned RF low-noise amplifiers

A gain stabilization technique for tuned integrated low-noise amplifiers (LNAs) is presented. The proposed method regulates the LC-tuned load impedance of the amplifier at the operation frequency against variations of passive devices in integrated circuit (IC) process. The impedance stabilization technique is based on the excellent relative accuracy of integrated resistors. Although the absolute deviation of the integrated resistors can be as large as ±20%, the relative deviation can be made smaller than ±1% provided that resistors are placed close to each other. By applying the proposed method, the voltage-gain variation of the inductively degenerated common-source LNA, which is the most popular LNA architecture, can be reduced several decibels. As a consequence, the entire radio receiver can more easily meet its specifications in the presence of IC process variations and the product yield is improved. Finally, besides the LNAs, the presented stabilization technique can also be utilized in other tuned amplifiers, filters or oscillators employing damped LC-tuned loads.