High linear dynamic range photoelectric sensor for blood oxygen detection

Abstract

The invention relates to a high-linearity dynamic range photoelectric sensor applied to blood oxygen detection. The photoelectric sensor comprises a differential operational amplifier A1, a differential operational amplifier Aau, a photoelectric diode array PD, a current mirror and a pulse frequency modulator PFM. The current mirror comprises an NMOS transistor M1, an NMOS transistor M2, an NMOS transistor M3 and an NMOS transistor M4. According to the photoelectric sensor, the technology of carrying out zero offset on the photoelectric diodes and adjusting offset voltages of the amplifiers to approach 0 through an amplifier monitoring mechanism is provided, the demand for a high-linearity dynamic range can be satisfied only by employing the single photoelectric diode, the area of a photoelectric sensor chip is greatly reduced, the cost is saved, the performance is clearly improved, and the photoelectric sensor is applicable to a high-precision blood oxygen detector system.

Description

technical field [0001] The invention belongs to the field of integrated circuit design, in particular to a high linear dynamic range photoelectric sensor applied to blood oxygen detection. Background technique [0002] Photoelectric sensors with high linear dynamic range are essential components of modern sensing systems. For example, a photoelectric sensor used in an oximeter must have a high dynamic linear response to light with wavelengths of 660nm and 940nm. For a high-precision blood oxygen concentration detector, more than 100dB photoelectric conversion linear dynamic range is required. From the perspective of cost saving, manufacturers prefer to realize the light sensor with a single photodiode. However, when the high dynamic range is extended to low light conditions, it is difficult to achieve because the dark current in a single photodiode is difficult to control and affects the linearity. The existing conventional technology is to use two photodiodes to realize ...

AI Technical Summary

Problems solved by technology

However, the performance of the photosensor under low light intensity is still restricted by the matching degree of the photodiode and the performance of the current mirror, especially when the reverse bias voltage on the photodiode is above hundreds of millivolts, the dark current of the photodiode will be greatly reduced at high temperature. raised

As a result, many industry products do not perform well in low light and high temperature conditions

Using an extra photodiode also significantly increases chip area and cost, as photodiodes are often several times the area of ​​other modules and introduce more thermal noise

High dynamic range can also be achieved with multi-sampling techniques, but at the expense of linearity

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