| Ultrasound diagnosis has received extensive attention and research because it has little harm to human body.With the development of the medical ultrasound imaging system toward the trend of low noise and low power consumption,the analog receiving front-end system has received extensive attention.In this paper,the CMOS low-noise amplifier(LNA)in the ultrasound imaging analog front-end receiving system is deeply studied and designed.This paper first analyzes the performance parameters of the CMOS low-noise amplifier,such as noise,linearity,impedance matching,and stability.Not only the S-parameter analysis for the two-port network analysis was introduced,but also the ultrasound imaging system was briefly analyzed.Among them,the types and characteristics of transducers,the characteristics and dynamic range of ultrasonic signals,and the power consumption requirements of the system are analyzed,which provide a theoretical basis for LNA design.Moreover,due to the large dynamic range,the TGC amplifier(Time Gain Compensation)is designed,which is following the stage of LNA.Based on the TSMC 0.18?m process,the gain of the TGC can be set to four values(0/12/26/40 d B).The design is based on the traditional wideband amplifier structure.Combining the shunt feedback structure with the common-gate structure,a shunt feedback/common-gate hybrid differential structure is implemented by using current reusing and gm enhancement techniques.This circuit can get good noise performance with low power consumption.Based on TSMC 0.18?m process,in the operating frequency 100 k Hz to 10 MHz,of the circuit,S11 is less than-12 d B,S22 is less than-20 d B,the gain is 13 d B,reverse isolation is less than-39.52 d B,noise figure is less than 2.65 d B,the input third-order intercept Point is-8.85 d Bm and the power consumption is 2m W.For the layout of the circuit layout,this paper uses a common core matching method on the core device.The layout area is 90?m*240?m.The designed LNA has good input and output matching,moderate gain,good reverse isolation,good linearity,good noise performance,and low power consumption.In addition,through the analysis of the transducer model,this paper proposes the ACC(Active Capacitive Cancellation Technology)which is different from the conventional ART(Active Resistive Termination)architecture.The low noise amplifier core amplifier adopts two-stage amplification stage,which is a PMOS folded cascode input stage and a class AB output stage.The circuit uses a common-mode feedback circuit to stabilize the common-mode voltage and high-swing bias circuit.At the same time,the bandgap reference circuit is designed to provide an “ideal” current source for the bias circuit.Based on the TSMC 0.18?m process,the ACC technology proposed in this paper and the traditional ART technology were compared and analyzed,and the optimal value of the ACC feedback capacitor was determined.In the operating frequency 100 k Hz to 10 MHz,the gain of the circuit is 17.85 d B,the input reference noise voltage power spectral density is.Finally,the layout of the circuit was designed,and the core of the amplifier was also adopted a symmetry-center matching method.The area of the layout was 290?m*130?m.The LNA performance of the proposed ACC LNA is higher than that of the conventional ART technology,and the gain is high and the noise performance is good.In summary,according to the requirements of the ultrasound imaging front-end system,two low-noise amplifiers and the following stage TGC circuit are designed,and the performance of each circuit is simulated and analyzed.In addition,the author also made layout designs based on the design requirements for the SFBCG hybrid structure amplifier and active capacitive cancellation amplifier. |
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