摘要
采用跨导线性化技术设计了一种具有指数增益特性的高线性中频可变增益放大器．该放大器由电流调节型可变增益单元、宽范围指数电压转换电路及固定增益放大器构成．基于0．25μm CMOS工艺的测试结果表明，放大器实现了8～48dB的增益连续变化，差分输出1V峰峰值下的三阶互调失真小于-60dBc，最大增益处噪声系数为8．7dB，50Ω负载下三阶输出截点为14．2dBm．
A highly linear intermediate frequency variable gain amplifier （VGA） with exponential gain control is developed using a transconductance linearization scheme. It consists of a variable-gain cell based on a current-steering structure, a novel wide-range exponential voltage generator, and a stage of a fixed-gain amplifier. The VGA is fabricated in 0. 25μm CMOS technology. Measurements show that a continuous-gain control range of 8-48dB and a 3rd intermodulation distortion of better than -60dBc at a differential output of 1V peak-to-peak are obtained. The noise figure at maximum gain is 8. 7dB, and the OIP3 loaded with 5012 is 14.2dBm.
