Electrotechnics self study notes 1.22

Non exam preparation materials
1.22

Chapter 16 Integrated operational amplifier

Application of operational amplifier in signal operation ：
1. Scale operation ： Inverting input ： Inverse proportional amplifier ; In phase input ： Voltage follower （ The following performance is better than the emitter output ）
2. Addition operation ： Control different volume levels of various music
3. Subtraction ： Make accompaniment tape
Application of operational amplifier in signal processing ：
1. Active power filter ： Frequency selection circuit , Choose useful signals , Suppress useless signals . Divided into low-pass 、 qualcomm 、 Band pass and band stop .
2. Sample and hold circuit
3. Voltage comparator ： Data monitoring 、 Auto-Control
Zero crossing comparator 、 hysteresis comparator , Hysteresis comparator has two advantages over zero crossing comparator ：1. It can accelerate the transformation process of output voltage ,2. The return difference improves the anti-interference ability of the circuit .

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1. Passive filter , also called LC filter , Using inductance 、 A filter circuit composed of a combination of capacitance and resistance , It can filter out one or more harmonics , The most common and easy to use passive filter structure is to connect inductor and capacitor in series .
2. Active power filter ： Because operational amplifiers are active devices , So it is called active filter , Its application can overcome LC The disadvantages of traditional harmonic suppression and reactive power compensation methods such as filters （ Traditional compensation can only be fixed ）, Realize dynamic tracking compensation , And it can supplement both harmonic and reactive power .
3. Sample and hold circuit ( sampling / Retainer ) Also known as sample and hold amplifier . When analog signals are A/D On conversion , It takes a certain conversion time , In this transition time , Analog signals should remain basically unchanged , Only in this way can the conversion accuracy be guaranteed . The sample and hold circuit is the circuit to realize this function .
4. The zero crossing comparator is used to detect whether an input value is zero . The principle is to use a comparator to compare two input voltages . One of the two input voltages is the reference voltage Vr, One is the voltage to be measured Vu. commonly Vr Connect from the positive phase input ,Vu From the inverting input . Output the forward or reverse saturation voltage according to the result of comparing the input voltage . When the reference voltage is known, the measurement result of the voltage to be measured can be obtained , When the reference voltage is zero, it is the zero crossing comparator .
5. Hysteresis comparator （ hysteresis comparator ） It is a comparator with hysteresis loop transmission characteristics . It can also be understood as a single limit comparator with positive feedback . Based on the inverse input single threshold voltage comparator, a positive feedback network is introduced , The inverse input hysteresis comparator with double gate limit is formed .