用于数字电视调谐芯片的高线性CMOS VGA

A Highly Linear CMOS VGA for Digital TV Tuner Chip

设计了一种适于DVB-C标准的中频可变增益放大器。该放大器由三部分构成:电流调节型可变增益单元、基于差分对管传输特性的指数控制电压产生电路以及一高线性输出级。采用Chartered0.25μm RFCMOS工艺库下流片。测试结果表明,4～49dB的连续增益范围,100MHz的3dB带宽,50Ω负载下的OIP3为16.8dBm。

An intermediate frequency （IF） variable gain amplifier （VGA） for DVB-C （Digital video broadcasting-cable） standard is presented in the paper. The VGA with exponential gain control is composed of a VGA core based on current-steering structure, an exponential voltage generator based on transfer characteristics of differential pair and a highly linear output stage. The VGA is fabricated in the Chartered 0.25μm RFCMOS technology. The measurement results indicate that 4-49 continuously gain range, about 100 MHz 3 dB bandwidth, OIP3 （3rd order utput intercept point） as high as 16.8 dBm with 50 Ω load are achived.