TMR Magnetic Sensor Low Noise Analog Front-End Detection Circuit Design

TMR magnetic sensors are detecting sensor of weak magnetic signals, in line with the sensor to detect substantial changes in magnetic field strength as much as possible, to achieve the highest possible dynamic range, its interface circuit must have a very low noise level.Secondly, with the development of integrated circuits, transistors are shrinking feature sizes and area, for the analog circuit design, the effect of offset and flicker noise will become more and more significant. In order to overcome these effects of integrated circuit development, design of analog circuits in future development will focus and intensity of research and development, to overcome this problem. Therefore, it can be predicted that in the future design of analog integrated circuits, low noise low offset technology will be widely used by the industry. The so-called rainy day ahead doing indepth research in this area is of great significance. Currently in the low offset low-noise in-amp circuit design, widely used technique is chopping and auto-zeroing. For structures to choose, capacitors-coupling and current feedback are the candidates. Although the instrumentation amplifiers development based on this foundation has made many achievements and progress, but there are still flaws and where further research is needed. Some suggestion given in this paper will attempt to solve these problems.This paper on the instrument amplifier low offset low-noise technology is discussed. Analysis of causes of the disorder and noise, in order to eliminate the disorder and the effects of low frequency noise, dual chopper-stabilization technique used in this paper, namely chopper with input stage and the system level. Chopper can make input stage offset voltage and low frequency noise can be reduced to a certain level, combined with system-level chopper used, low frequency noise can be further reduced. Double chopper technology use can greatly improve noise performance. Ripple problems with the chopper through this ripple restraint loop elimination. Ripple design of restraint loop to replace difficult use low-pass filter. In addition, in order to reduce the impact of the gain error and gain error compensation strategy was designed, DEM(Dynamic Element Matching) and GEC(Gain Error Correction) loops, complete the gain error compensation.In addition, in this paper, also implements the Delta-Sigma modulator design, instrumentation amplifier and modulator combined, achieve a digital stream output. Finally, we completed the design of integrated circuits and layout design and rendering work.The post simulation results of this thesis are: 1Hz the equivalent input noise 8nV ? √ Hz or less, flicker noise corner frequency less than or equal to 0.7mHz. Δ∑ modulator is the number of significant digits is 21.