一种应用于CMUT的高增益低噪声跨阻放大器

A High Gain Low Noise Transimpedance Amplifier for CMUT

设计了一种应用于微电容超声换能器(CMUT)的高增益、低噪声跨阻放大器。采用调节型共源共栅结构作为跨阻放大器的输入级,实现了低输入阻抗、宽频带,有效隔离了CMUT的静态电容和输入寄生电容对带宽的影响。输出级采用两级反相放大器,实现了高增益,提高了带负载能力。基于GF 0.18μm CMOS工艺,电路采用Cadence Spectre软件进行仿真。结果表明,低频跨阻增益为115.5 dB·Ω,单位增益频率为1.65 GHz,-3 dB带宽为10 MHz,等效输入电流噪声为1.1 pA·Hz-1/2@1 MHz,能满足CMUT工作频率200 kHz^2 MHz的带宽要求和微弱电流信号的检测要求。该电路采用正负3.3 V供电,功耗为98 mW,芯片尺寸为145μm×115μm。

A high gain and low noise transimpedance amplifier was designed for the applications of capacitive micromachined ultrasonic transducer(CMUT).A regulated cascode structure was used as the transimpedance amplifier input stage for the circuit,which had realized low input impedance and broadband,and had cancelled effectively the effects of static capacitance and input parasitic capacitance of CMUT on the bandwidth.Two-stage inverting amplifiers were used at the output stage to achieve high gain and improve the drive load capacity.Based on GF 0.18μm CMOS technology,the transimpedance amplifier was simulated using Cadence Spectre softwares.The results showed that the low frequency transimpedance gain reached 115.5 dB·Ω,the unity gain frequency was 1.65 GHz,the-3 dB bandwidth was 10 MHz and the equivalent input current noise was 1.1 pA Hz-1/2@1 MHz,which had met the bandwidth requirements of CMUT’s operating frequency of 200 kHz^2 MHz and the detection requirements of weak current signal.The circuit was powered by 3.3 V,the power consumption was 98 mW,and the chip area was 145μm×115μm.