1 Introduction
In recent years, electronic products using batteries as power sources have been widely used, and designers are eager to use low-voltage analog circuits to reduce power consumption. Low voltage, low power, low noise analog circuit design technology is becoming a research hotspot. From the perspective of energy conservation, low power consumption is not only the demand for battery-powered portable devices, but even for large systems that use utility power, it can not only extend the use time of equipment, but also delay the aging of equipment. The importance of operational amplifiers as the most basic unit in integrated circuits is well known. In a low-voltage operational amplifier, the dynamic range of the signal is reduced due to a decrease in the supply voltage. At the same time, the amplitude of the noise signal is relatively increased, and the signal-to-noise ratio of the amplifier is reduced. To solve these design problems, Dior Microelectronics has developed several low-power, low-noise op amps to meet this market demand.
2. Background
With the rapid development of the medical electronic device industry, mobile handheld medical electronic devices for personal health care are also rapidly developing. Whether it's a handheld defibrillator or a dynamic blood glucose monitor, designing such a product is not an easy task. Choosing the right components to meet design specifications, minimizing costs, ensuring the power of the design, paying particular attention to the actual size of the product, etc., are issues that must be considered during the product design process. Similarly, with the improvement of the security awareness of Chinese people, smoke detection equipment has entered thousands of households, and has put forward higher requirements for the design of fire protection products with low power consumption (long battery life) sensitivity and high reliability.
Whether it's temperature, pulse, blood glucose reading or other biosensors, implementing the appropriate signal amplification and conditioning links is the most important issue. In an analog front-end circuit, an op amp is the most critical unit. In this circuit, an op amp with low noise, high precision, low power consumption, and low bias current is generally selected. The first stage of the signal chain typically uses a high common-mode rejection ratio, a low bias current (especially for infrared tube sensors), and a low-noise op amp; the second stage uses a low-power, high-precision, low-noise op amp. The next stage of the signal chain is a good delta-sigma or successive approximation analog-to-digital converter (ADC). Features such as single-cycle filter settings and on-demand conversion simplify the ADC design requirements, increase conversion speed, and provide large source impedance. With proper layout and component selection, a clean, accurate and meaningful signal can be input to the system microprocessor/DSP.
Smoke structure block diagram
An alarm device consisting of a smoke sensor can report a fire alarm in time. In the smoke sensor, a semiconductor material that is particularly sensitive to smoke gas, such as tin oxide, zinc oxide, etc., is also installed, and they are also referred to as gas-sensitive materials. In a smog-like environment, when the concentration of the smog reaches a certain amount, the resistance inside the gas-sensitive material drops rapidly. Once the smoke disappears, their resistance will return to normal. Another method of detecting smoke is to use the principle that the infrared light is blocked by the smoke to cause the infrared to receive the current change and alarm. The photoelectric method is divided into forward scatter and back scatter detection. The sensor is installed in the optical maze. When there is no smoke, the sensor can not receive or only receive a very weak optical signal. After amplification by the amplifier, the logic judgment circuit does not perform alarm processing. When smoke enters the maze, the light illuminates the smoke particles to produce scattering. The sensor receives a relatively strong optical signal. After amplification, the logic alarm circuit sends an alarm signal. In these applications, op amps are key components that require ultra-low power, low bias current, and low noise.
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