BACKGROUND One of the major concerns in implantable optoelectronics is the heat generated by emitters such as light emitting diodes (LEDs). Such devices typically produce more heat than light, whereas medical regulations state that the surface temperature change of medical implants must stay below + 2 °C. The LED's reverse current can be employed as a temperature-sensitive parameter to measure the temperature change at the implant's surface, and thus, monitor temperature rises. The main challenge in this approach is to bias the LED with a robust voltage since the reverse current is strongly and nonlinearly sensitive to the bias voltage. METHODS To overcome this challenge, we have developed an area-efficient LED-based temperature sensor using the LED as its own sensor and a CMOS electronic circuit interface to ensure stable bias and current measurement. The circuit utilizes a second-generation current conveyor (CCII) configuration to achieve this and has been implemented in 0.35 μm CMOS technology. RESULTS The developed circuits have been experimentally characterized, and the temperature-sensing functionality has been tested by interfacing different mini-LEDs in saline models of tissue prior to in vivo operation. The experimental results show the functionality of the CMOS electronics and the efficiency of the CCII-based technique with an operational frequency up to 130 kHz in achieving a resolution of 0.2 °C for the surface temperature up to + 45 °C. CONCLUSIONS We developed a robust CMOS current-mode sensor interface which has a reliable CCII to accurately convey the LED's reverse current. It is low power and robust against power supply ripple and transistor mismatch which makes it reliable for sensor interface. The achieved results from the circuit characterization and in vivo experiments show the feasibility of the whole sensor interface in monitoring the tissue surface temperature in optogenetics.

中文翻译：

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一种电流模式系统，可自我测量植入式光电器件上的温度。

背景技术可植入光电器件中的主要关注之一是由诸如发光二极管（LED）的发射器产生的热量。这种设备通常产生的热量多于光，而医学法规规定，医用植入物的表面温度变化必须保持在+ 2°C以下。LED的反向电流可用作温度敏感参数，以测量植入物表面的温度变化，从而监控温度升高。这种方法的主要挑战是用稳定的电压偏置LED，因为反向电流对偏置电压强烈且非线性敏感。方法为了克服这一挑战，我们已经开发了一种面积小的基于LED的温度传感器，使用LED作为其自己的传感器和CMOS电子电路接口，以确保稳定的偏置和电流测量。该电路利用第二代电流传输器（CCII）配置来实现这一目标，并已采用0.35μmCMOS技术实现。结果已对开发的电路进行了实验表征，并且在体内操作之前通过在组织的盐水模型中连接不同的微型LED来测试温度感应功能。实验结果表明，CMOS电子器件的功能以及基于CCII的技术的效率（工作频率高达130 kHz）在表面温度高达+ 45°C时达到0.2°C的分辨率。结论我们开发了强大的CMOS电流模式传感器接口，该接口具有可靠的CCII，可以准确地传递LED的反向电流。它具有低功耗和鲁棒性，可抵抗电源纹波和晶体管失配，从而使其对于传感器接口十分可靠。通过电路表征和体内实验获得的结果表明，整个传感器接口在光遗传学中监测组织表面温度的可行性。