运算放大器与电压比较器的区别和应用案例_比较器和运算放大电路的区别资源-CSDN文库

运算放大器

5星 · 超过95%的资源需积分: 10 170 浏览量 2022-11-14 20:09:28 上传评论收藏 1.33MB PDF 举报

资源详情

资源评论

1/51

Application Note

64AN070E Rev.007

Jun.2021

Op-Amp/Comparator Application Note

Operational amplifier ,Comparator (Tutorial)

This application note explains the general terms and basic techniques that are necessary for configuring application circuits with

op-amps and comparators. Refer to this note for guidance when using op-amps and comparators. a

Contents

What Is Op-Amp/Comparator? .......................................................................................................................................................................... 2

1.1

What is op-amp? ......................................................................................................................................................................................... 2

1.2

What is comparator? .................................................................................................................................................................................. 3

1.3

Internal circuit configuration of op-amp/comparator ............................................................................................................................ 4

Absolute Maximum Rating ................................................................................................................................................................................ 5

2.1

Power supply voltage/operating range of power supply voltage ....................................................................................................... 5

2.2

Differential input voltage ............................................................................................................................................................................ 6

2.3

Input common-mode voltage .................................................................................................................................................................... 7

2.4

Input current ................................................................................................................................................................................................. 8

2.5

Operating temperature range .................................................................................................................................................................... 8

2.6

Maximum junction temperature, storage temperature range .............................................................................................................. 8

2.7

Power dissipation (total dissipation) ........................................................................................................................................................ 9

Electrical Characteristics .................................................................................................................................................................................. 10

3.1

Supply current ........................................................................................................................................................................................... 10

3.2

Input offset voltage ................................................................................................................................................................................... 12

3.3

Input bias current and input offset current ........................................................................................................................................... 16

3.4

Input common-mode voltage range ....................................................................................................................................................... 18

3.5

Maximum output voltage (High/Low level output voltage ................................................................................................................. 20

3.6

Large signal voltage gain (open loop gain) .......................................................................................................................................... 22

3.7

CMRR (Common Mode Rejection Ratio)............................................................................................................................................... 23

3.8

PSRR (Power Supply Rejection Ratio) .................................................................................................................................................. 27

3.9

SR (Slew Rate) ........................................................................................................................................................................................... 30

3.10

Frequency characteristics of op-amp .................................................................................................................................................... 31

3.11

Phase delay and oscillation ..................................................................................................................................................................... 33

3.12

Cause of phase delay in op-amp ............................................................................................................................................................ 35

3.13

Stability confirmation method (amplifier circuit) .................................................................................................................................. 36

3.14

Stability confirmation method (unity feedback circuit/voltage follower) ......................................................................................... 37

3.15

Summary of stability confirmation method .......................................................................................................................................... 38

3.16

Countermeasures against oscillation by load capacitance (output isolation resistor 1) ............................................................. 38

3.17

Countermeasures against oscillation by load capacitance (output isolation resistor 2) ............................................................. 39

3.18

THD+N (Total Harmonic Distortion + Noise) ......................................................................................................................................... 40

3.19

Input referred noise ................................................................................................................................................................................... 44

3.20

Response time (rise/fall times and propagation delay time).............................................................................................................. 48

Reliability Items .................................................................................................................................................................................................. 50

4.1

Electrostatic Breakdown Voltage (ESD Breakdown Voltage) ............................................................................................................ 50

4.2

Latch Up Test ............................................................................................................................................................................................. 51

2/51

Application Note

Op-Amp/Comparator Tutorial

64AN070E Rev.007

Jun.2021

1 What is Op-Amp/Comparator?

1.1 What is op-amp?

An op-amp (operational amplifier) is a differential amplifier

that has high input resistance, low output resistance, and high

open loop gain. Its function is to amplify the differential

voltage between the + input terminal (non-inverting terminal)

and the - input terminal (inverting terminal).

Each op-amp circuit is composed of five terminals: a power

supply terminal on the positive side, a power supply terminal

on the negative side, a + input terminal, a - input terminal, and

an output terminal. (There are no general terms for the

terminals except classifications such as power source, input

and output.)

Table 1.1.1. Examples of names for op-amp

power supply terminals

Bipolar type CMOS type

Power supply

terminal on the

positive side

VCC VDD

Power supply

terminal on the

negative side

VEE VSS

Providing high input resistance (impedance) and low output

resistance is a function required for the op-amps.

In Figure 1.1.2. Model of voltage controlled voltage source

amplifier (op-amp), V

is the input signal source, R

is the

signal source output resistor, R

is the input resistor of the

op-amp, R

is the output resistor of the op-amp, R

is the load

resistor, and A

is the amplification factor of the op-amp. The

relation between the input and output voltages is described in

the equation (1.1.1).

(1.1.1)

As shown in Figure 1.1.2 and the equation (1.1.1), the signal

voltage V

is divided into resistance voltages by the signal

source resistor R

and the input resistor R

of the op-amp. As

a result, the input signal to the op-amp is attenuated.

However, when the R

is sufficiently larger than the R

∞), the first term in the equation (1.1.1) can be approximated

by 1 and it can be considered that V

= V

. Next, as for the

second term, the amplified input voltage A

is divided by the

output resistor R

of the op-amp and the load resistor R

and

output in Figure 1.1.2.

Here, the signal can be output without being attenuated if the

is sufficiently smaller than the R

=0) because the

second term can be approximated by 1. Such an op-amp is

called an ideal op-amp. Usually, op-amps with high input

resistance and low output resistance are preferred. The

circuit configuration is designed to achieve an ideal op-amp

as closely as possible.

Table 1.1.2. Ideal input and output resistances required

for op-amp

Input

resistance

Output

resistance

Ideal op-amp

(Voltage controlled

voltage source)

∞

Figure 1.1.1. Op-amp/comparator symbol

Figure 1.1.2. Model of voltage controlled voltage source

amplifier

Power supply terminal on the

positive side (VCC)

Power supply terminal on

the negative side (VEE)

Output (OUT)

+ input terminal

(+IN)

- input terminal

(-IN)









3/51

Application Note

Op-Amp/Comparator Tutorial

64AN070E Rev.007

Jun.2021

VIN+

VOUT

VIN-

An op-amp amplifies a small differential voltage between the

+ input terminal and - input terminal and outputs the amplified

voltage. For this purpose, an op-amp with a large

amplification factor is preferred. The reason is explained

using the voltage follower circuit in Figure 1.1.3.

A voltage follower circuit is a circuit in which the input and

output voltages are equal. It is mainly used as a voltage

buffer.

This circuit provides characteristics such as high input

resistance and low output resistance, as mentioned above.

In Figure 1.1.3, the input voltage V

and the V

OUT

become

identical.

Figure 1.1.3. Voltage follower circuit

Since the op-amp amplifies the differential voltage between

the terminals by the amplification factor of the op-amp, the

output voltage is expressed with the equation (1.1.2).

(1.1.2)

The equation (1.1.2) is converted to the equation (1.1.3).

(1.1.3)

In the equation (1.1.3), when the open loop gain of the

op-amp is sufficiently high, the left side can be approximated

by 0 and the equation gives V

= V

OUT

. When the gain is low,

the left side of the equation (1.1.3) cannot be approximated

by 0 and the output voltage will contain an error.

An op-amp with a high open loop gain is desirable because

the error in the output voltage can be minimized by the high

gain.

From another point of view, the high open loop gain means

that the difference in the potentials between the + input

terminal and the - input terminal is minimized. Namely, the

higher the open loop gain is, the better the relation V

IN+

= V

IN-

holds. This relation in which the potentials of the + input

terminal and the - input terminal become nearly equal is

called a virtual short-circuit, imaginary short-circuit, or virtual

grounding. When configuring and using a negative feedback

circuit, this relation is realized and application circuits are

designed utilizing the characteristic of the virtual grounding.

1.2 What is comparator?

A comparator (voltage comparator) has the same terminal

structure as an op-amp composed of five terminals: the +

input terminal, the - input terminal, the positive side power

supply terminal, the negative side power supply terminal, and

the output terminal. When a comparator is used, the voltage

is fixed at one of the input terminals as a reference terminal,

and the difference between the reference voltage and the

output voltage to the other terminal is amplified. The output

voltage is either higher or lower than the reference voltage.

When the + input terminal potential > the

- input terminal

potential

→ High level output.

When the

- input terminal potential > the + input terminal

potential

→ Low level output.

The major difference between op-amps and comparators is

whether or not the phase compensation capacitance exists.

Since op-amps configure and utilize a negative feedback

circuit, they require phase compensation capacitance to

prevent oscillation inside the IC. On the other hand, since

comparators will not configure the negative feedback circuit,

they do not include the phase compensation capacitance.

Since the phase compensation capacitance limits the

response time between the input and the output, a

comparator without the phase compensation capacitance

provides a better responsiveness compared to an op-amp.

In contrast, if an op-amp is used as a comparator, since the

phase compensation capacitance limits the response, it

provides a very poor responsiveness compared with a

comparator.

Therefore, care must be taken when using an op-amp as a

comparator.

)()(

OUTSVININVOUT

VVAVVAV 



OUTS

OUT



4/51

Application Note

Op-Amp/Comparator Tutorial

64AN070E Rev.007

Jun.2021

Figure 1.3.2. Internal circuit configuration of comparator

Figure 1.3.1. Internal circuit configuration of op-amp

入力段

利得段

出力段

+入力端子

(+IN)

-入力端子

(-IN)

出力端子

(OUT)

入力段

利得段

出力段

+入力端子

(+IN)

-入力端子

(-IN)

出力端子

(OUT)

位相補償容量

(a) Internal circuit configuration of general op-amp

(a) Internal circuit configuration of general comparator

OUT

VEE

VCC

+IN

-IN

入力段利得段

出力段

(b) BA2903 Internal equivalent

OUT

VEE

VCC

+IN

-IN

入力段利得段出力段

位相補償容量

(b) BA4558 Internal equivalent

1.3 Internal circuit configuration of

op-amp/comparator

Figure 1.3.1 shows the internal circuit configuration of an

op-amp. Generally, an op-amp is composed of three stages:

the input stage, the gain stage, and the output stage.

The input stage is configured with a differential amplification

stage that amplifies the differential voltage between the two

terminals. In addition, it does not amplify the common-mode

signal component (a condition where no difference in

potential exists between the terminals and an equal voltage is

input).

Since the gain is insufficient with the differential amplification

circuit alone, the gain stage further increases the open loop

gain in the op-amp.

In general op-amps, the phase compensation capacitance for

oscillation prevention is connected over the gain stage.

The output stage is connected as a buffer so that the op-amp

characteristics will not be affected by loads such as the

resistance connected to the output terminal. The changes in

the output characteristics due to the loads (such as distortion

or voltage drop) mainly depend on the circuit configuration

and the current capability of the output stage. The type of

output stage, Class A and B, C, or AB push-pull output circuit,

is classified according to the amount of drive current flowing

in the output circuit (the difference in the bias voltage).

The difference in the amount of drive current affects the

distortion factor generated in the output stage. In general, the

Class A output circuit has the lowest distortion factor, followed

by Classes AB, B, and C.

Figure 1.3.2 shows the internal circuit configuration of a

comparator. Although the circuit configuration is nearly

identical to that of an op-amp, the phase compensation

capacitance for oscillation prevention is not included in the

comparator since it is not supposed to be used in a negative

feedback configuration. Since the phase compensation

capacitance limits the operating speed between the input and

the output, the response time is remarkably better compared

with op-amps.

The type of output circuit for comparators is classified into the

open collector (open drain) type or the push-pull type.

Figure 1.3.2 (b) shows the internal equivalent circuit of the

BA2903. The BA2903 is an output circuit of the open collector

type.

Input

stage

Gain

stage

Input

stage

Input stage

Gain stage

Output

stage

Output

stage

Output terminal

(OUT)

- input terminal

(-IN)

Output

stage

Output terminal

(OUT)

- input terminal

(-IN)

Gain

stage

Output

stage

+ input terminal

(+IN)

Phase compensation

capacitance

+ input terminal

(+IN)

Phase compensation capacitance

5/51

Application Note

Op-Amp/Comparator Tutorial

64AN070E Rev.007

Jun.2021

Note: Dual power supply refers to the application of a power supply voltage to op-amps using two voltage power supplies (positive and negative).

Single power supply refers to the application of a power supply voltage to op-amps with reference to the ground.

2 Absolute Maximum Rating

The absolute maximum rating is specified in the data sheet

for op-amps/comparators. The absolute maximum rating

provides the condition that must not be exceeded even

instantaneously. The application of a voltage above the

absolute maximum rating or use in a temperature

environment outside the environment specified by the

absolute maximum rating may cause the deterioration of

characteristics or destruction of the internal circuit. The

absolute maximum ratings for the following items are

explained.

2.1. Power supply voltage/operating range of power supply

voltage

2.2. Differential input voltage

2.3. Input common-mode voltage

2.4. Input current

2.5. Operating temperature range

2.6. Maximum junction temperature, storage temperature

range

2.7. Power dissipation (total dissipation)

2.1 Power supply voltage/operating range of

power supply voltage

For the power supply voltage, the absolute maximum rating

refers to the maximum power supply voltage that can be

applied between the positive side power supply terminal

(VCC terminal) and the negative side power supply terminal

(VEE terminal) of the op-amp without causing the

deterioration of characteristics or destruction of the internal

circuit. Figure 2.1.1 shows examples of the power supply

voltage that can be applied to an op-amp/comparator that has

an absolute maximum rating for the power supply voltage of

36 V. The absolute maximum rating for the power supply

voltage specifies the difference in voltage between the VCC

and VEE terminals. The op-amp/comparator must be used

with the value of (VCC-VEE) never exceeding the absolute

maximum rating for the power supply voltage. Therefore,

when 24 V and -12 V are applied to the VCC and VEE

terminals, respectively, the difference in voltage between the

terminals is 36 V and the deterioration of characteristics or

destruction does not occur. It should be noted that the

absolute maximum rating for the power supply voltage has a

different meaning from the operating power supply voltage.

The absolute maximum rating for the power supply voltage

indicates the maximum value of the power supply voltage that

will not cause the characteristics deterioration or destruction

of the IC. It does not provide the voltage range in which the

specifications and characteristics that are described in the

data sheet are maintained. To obtain the characteristics that

are guaranteed in the specifications, the op-amp/comparator

must be used with the voltage value within the operating

range of the power supply voltage. However, the absolute

maximum rating for the power supply voltage of some

products may be identical to the maximum value of the

operating power supply voltage. Op-amps are sometimes

called dual power supply or single power supply op-amps. In

other words, an op-amp may be suited for the usage as a

dual power supply or single power supply. Dual power supply

op-amps have a voltage range in which either the input

voltage or the output voltage cannot be output due to the

circuit configuration on the positive power supply (VCC) side

and the negative power supply (VEE) side. Therefore, the

dual power supply op-amps are often used while applying a

positive power supply and a negative power supply with the

ground being the middle point. On the other hand, the single

power supply op-amps are used while applying the positive

power supply with reference to the ground and the

input/output can be performed nearly at the ground level.

OUT

VEE=-18V

VCC=18V

OUT

VEE=GND

VCC=36V

OUT

VEE=-12V

VCC=24V

VCC-VEE=18V-(18V)=36V

Dual power supply, ±18 V applied

VCC-VEE=36V-(0V)=36V

Single power supply, 36 V applied

VCC-VEE=24V-(-12V)=36V

Dual power supply, 24 V and -12 V applied

Figure 2.1.1. Examples of the power supply voltage that can be applied to an IC that has an

absolute maximum rating for the power supply voltage of 36 V

剩余51页未读，继续阅读

评论收藏

内容反馈

忧伤的石一

2023-07-27

这篇文件详细介绍了运算放大器与电压比较器之间的区别和应用案例，信息清晰明了，容易理解。

运算放大器与电压比较器的区别和应用案例

评论5

最新资源

运算放大器与电压比较器的区别和应用案例

评论5

最新资源

相关推荐

资深工程师设计案例： 扒一扒运算放大器

AD603增益可调运算放大器的工作原理和应用详细说明

模电数电multisim仿真实例

Arduino光敏电阻传感器模块开发实例源码

Multisim设计Multisim基础仿真电路200例.zip

ewb multisim 仿真实例电路图全集

Ewb5.12电子电路仿真软件中文版含200实例及中文教程

multisim12清华大学本科教育所用的例子

msp430书稿开发板

晶体管式电流传感器的识别

传感技术中的晶体管式电流传感器的识别

基于 AVR 的单片嵌入式系统原理与实践应用

现代直流伺服控制技术及其系统设计

STM32CubeMx6.4.0版本+JRE安装包

KEIL5 常用stm32芯片包下载

ser2pl64.sys是电脑重要系统文件，主要用于串口转USB，描述：USB-to-Serial Cable Driver

CubeMX，6.11版本

嵌入式入门-ADS-安装包

“ 官网 ”最新版-《Arm Compiler 5.06 update 7 (build 960) Lin32》

Keil.STM32F4xx-DFP.2.17.1

第十五届蓝桥杯嵌入式组省赛完整工程

RK3588全套硬件设计资料

squareline最新1.4.0版本(适用windows)

Keil5.33的STLink文件

stm32g474ret6中文参考手册

STM32CubeMx 6.1.1版本+JRE安装包

第十四届蓝桥杯省赛电子类嵌入式组完整工程代码

ARMCC Compiler Verdion 5编译器

野火visio波形工具箱【0积分】

资深工程师设计案例：扒一扒运算放大器