Research On The Readout Circuit Of Low-noise Uncooled Infrared Detector

Uncooled infrared detection technology is an important member of infrared imaging,which has important applications in the military and civil fields.Compared with the refrigeration type infrared detector technology,it has the advantages of low price,low power consumption and small volume.With the continuous development of infrared imaging technology,the performance requirements of infrared detection technology are also increasing.As a part of the infrared detection system,the noise performance of the readout circuit largely determines the imaging quality of the system,so it is very important to study the low noise readout circuit.The research content of this paper is as follows:1.In this paper,the main noise sources of the infrared focal plane are analyzed,and the main noise sources of the circuit are input level integrated operational amplifier noise,reset KTC noise and fixed pattern noise(FPN).On this basis,two main external noise reduction technologies are studied and designed.2.The input stage is the main source of noise,while the op amp contributes most of the noise of the input stage.In this paper,a two-stage op amp structure with PMOS as the differential input is designed.By adding an improved CMOS switch chopper to the op amp,the noise in the low frequency part of the circuit can be effectively reduced and the common mode noise of the circuit can be suppressed.Compared with the traditional operational amplifier,the noise of the circuit is reduced from 0.14 mv to 0.038 mv.3.In the column readout stage,a correlated double sample(CDS)circuit is designed according to the characteristics of the pixel unit.The noise of the sampling voltage in the column readout stage is effectively reduced by optimizing the structure and working sequence of the CDs circuit.In addition,the output buffer circuit uses a five transistor operational amplifier with low noise to reduce the noise.The simulation results show that the circuit can work at the clock frequency of 5MHz,the output swing is 3V,the single column power consumption is 0.245 mv,the maximum frame frequency is 60 Hz,and the output noise is only 0.174 mv,which meets the design requirements.4.Due to the complex fabrication process and high cost of vanadium oxide(VOX)film in infrared detector,an equivalent pixel circuit structure for 640 × 480 uncooled infrared detector readout circuit is designed in this paper.The structure of the circuit can be tested before the fabrication of vox film,so as to eliminate the chips that have failed in the readout circuit,so as to reduce the fabrication cost of the infrared detector.