Research Of Infrared Focal Plane Array Readout Circuit With Background Suppression

Uncooled infrared imaging technology is widely used in military, industrial, medical and other fields. Infrared focal plane array detector, which is the core of the infrared imaging system, is composed of detector arrays and readout circuit, compared with the traditional infrared detector, it has a simple structure, high performance, good reliability, etc. Therefore, researching uncooled infrared focal plane array readout circuit has important practical significance.For the weak signal detected by uncooled infrared focal plane detector, on the basis of 0.35 um process model, this paper designed the analog circuits of the uncooled infrared focal plane array readout circuit. Signal is amplified in the circuit with the cooperation of timing, the noise is removed, the output buffer is achieved after sampled,the circuit lays a good foundation for uncooled infrared detector circuit to realize the corresponding function.First of all, according to the physical characteristics of focal plane photosensitive pixels, on the basis of NMOS buffer injection bias circuit, the circuit makes pixels in a state of constant voltage offset, flow of electricity output is changing with temperature. Because the current output is very weak, this paper designs a folded cascode operational amplifiers, the amplifier improves the efficiency of the injection of the signal, as well as the signal is amplified, reduces the performance requirements for the subsequent signal processing. Because the current output have a large background noise, background suppression circuit is responsible for the elimination of background noise signals in the infrared signal. This paper introduces and designs a new type of background suppression circuit, introduces the concept of the first generation of switch current circuit(SI) to readout circuit. By setting the appropriate proportion of MOS tube, the circuit realizes the function of current copy. The circuit controls switches by using the appropriate timing, The circuit stores and copies noise signal firstly, and then the pixels output signal subtract noise signal, at last, the circuit achieves the purpose of removing background noise signal, which can effectively improve the SNR of the system and the ability to identify the weak signal. After eliminating the background noise, electrical flow through the integral amplifier module circuit, sampling and holding circuit, finally is sent to the subsequent circuit after a buffer. In this paper digital timing circuits is designed, this article lists the circuit structures and the simulation results of the various unit circuits and the whole circuit. Finally, according to standard 0.35 um N well CMOS process model, this paper designs the layout of the readout circuit.After simulation though Spectre in Cadence, the result shows that, after denoising and amplification, the analog readout circuit can extract small signal detected by pixels efficiently under the control of the timing signal. The proportion of current replication is approximately 94%. In this article, the designed circuit can detect the signal change caused by the temperature range of 10℃ to 50℃, the area of analog readout circuit layout is approximately 300μm x 300 um, The circuit provides a certain basis for the integration of infrared focal plane array readout circuit of single chip.