I. Introduction

1. Advance statement

The following refers to the teaching materials of Harbin Institute of Technology, and the following "teaching materials" refer to the teaching materials of Harbin Institute of Technology
Red indicates important places ; orange indicates less important places ; brown indicates important concept names .

2. Learning perception

It is mainly divided into two parts: linear application circuits (various operations and signal processing circuits) and nonlinear application circuits (comparators and their application circuits).
There are many circuits in this chapter, and you need to memorize a lot of basic circuits for easy problem solving.
In this chapter, the superposition theorem is often used to analyze the situation of multiple input voltages.
Because there are too many types, the exercises and notes in this chapter are combined together and are not specially placed.

2. Text

1. Linear application

The operational amplifier is in a closed- loop working state and introduces negative feedback , which has the characteristics of virtual short and virtual break .

(1) Proportional operation circuit

①Inverse proportional operation circuit

$u_{o}=-\frac{R_{f}}{R_{1}}u_{i}$

②Same-phase proportional operation circuit

$u_{o}=(1+\frac{R_{f}}{R_{1}})u_{i}$

③Differential proportional operation circuit (subtraction operation circuit)

$u_{o}=\frac{R_{f}}{R_{1}}(u_{I1}-u_{I2})$

(2) Addition and subtraction circuit

①Inverting input summing circuit

$u_{o}=-(\frac{R_{f}}{R_{1}}u_{I1}+\frac{R_{f}}{R_{2}}u_{I2})$

②Addition and subtraction circuit

(3) Integral and differential operation circuit

①Integral operation circuit

$u_{o}=-\frac{1}{RC} \int u_{I} dt$

② Differential operation circuit

$u_{o}=-RC \frac{du_{c}}{dt}$

(4) Logarithmic and exponential operation circuits

①Logarithmic operation circuit

$u_{o}=-U_{T}ln\frac{u_{I}}{I_{S}R}$

② Exponential operation circuit

$u_{o}=-RI_{S}exp(\frac{u_{I}}{U_{T}})$

(5) Multiplication, division, square root

In the operation circuit composed of analog multipliers and integrated operational amplifiers, it is necessary to first judge whether negative feedback is formed , and then the circuit can be analyzed by virtual short and virtual break.

①Multiplication circuit

②Division operation circuit

③ Square root operation circuit

(6) Absolute value operation circuit

(7) Active filter

①First-order low-pass filter

②Second-order low-pass filter

③ Active high-pass filter

④ Active bandpass filter

⑤ Active band-stop filter

2. Nonlinear applications

The op amp is in an open-loop working state or has introduced positive feedback , which has the characteristics of virtual break .

【Model Note】6. Integrated Operational Amplifier Application Circuit

I. Introduction

1. Advance statement

2. Learning perception

2. Text

1. Linear application

(1) Proportional operation circuit

(2) Addition and subtraction circuit

(3) Integral and differential operation circuit

(4) Logarithmic and exponential operation circuits

(5) Multiplication, division, square root

(6) Absolute value operation circuit

(7) Active filter

2. Nonlinear applications

(1) Single limit comparator

(2) Hysteresis comparator

(3) Window comparator

(4) Rectangular wave generating circuit

(5) Triangular wave generating circuit

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