一种带消失调电路的dB线性可变增益放大器设计

Design of A dB-linear Variable Gain Amplifier with DC Offset Cancellation

设计实现了一种增益连续型的dB线性中频可变增益放大器.该放大器由2级优化了线性度的可变增益单元级联而成,通过宽范围的指数增益产生电路的设计,实现放大器的增益与控制电压成dB线性;同时,还设计了1种连续时间型Gm-C反馈结构的消直流失调电路,可实时抑制放大器的输出直流失调电压.电路采用0.18μm CMOS工艺进行流片,测试结果表明,在3.3V电压下,连续增益动态范围为-10-46dB,-3dB带宽大于20 MHz,直流失调的抑制增益小于-5dB,核心电路面积仅为0.11mm2.

An intermediate frequency variable gain amplifier with continuous, decibel linear gain variation has been designed. It consisted of two stages of variable gain cells which optimized the nonlinear distortion, as well as a wide-range exponential generator to achieve the dB-linear characteristic. A continuous time Gm-C chain was also described for DC offset cancellation. The circuit was fabricated in 0.18 μm CMOS process. Measure- ment results show that, under 3.3 V supply, the continuous gain range is from --10 dB to 46 dB, --3 dB band width is more than 20 MHz and the suppression gain for DC offset is less than --5 dB. The VGA circuit occu- pies only 0.11 mm2.