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Jan 19 2018

Operational Amplifier Characteristics,Classification,Main parameters and Types

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Summary

It has been more than 40 years since the analog operational amplifier was born. The earliest process is the use of silicon NPN process, later improved to silicon NPN-PNP process (hereafter called standard silicon process). After the technology of junction field effect transistor(JFET) matured, it was further added with the JFET process. When the MOS tube technology matured. especially after the CMOS technology matured, the analog operational amplifier has made a qualitative leap. This paper is mainly talking about the classification and characteristics of operational amplifier,including its main parameters,common operational amplifier typers and etc..


Article coreOperational Amplifier Characteristics,Classification,Main parameters and TypesMaterialVacuum tube
English nameOperational Amplifier 

Category

Semiconductor/Amplifier
main parameterCommon mode suppression , gain bandwidth product and etc.



Catalogs


Catalogs

I.Classification and Characteristics of Operational Amplifier (op amp)

2.1 DC parameter

1.1 Classification based on manufacturing process

2.2 AC parameter

1.2 Classification based on function / performance

III.Common Operational Amplifier Types

II.The Main Parameters of Operational Amplifier





Introduction

I.Classification and Characteristics of Operational Amplifier (op amp)

It has been more than 40 years since the analog operational amplifier was born. The earliest process is the use of silicon NPN process, later improved to silicon NPN-PNP process (hereafter called standard silicon process). After the technology of junction field effect transistor(JFET) matured, it was further added with the JFET process. When the MOS tube technology matured. especially after the CMOS technology matured, the analog operational amplifier has made a qualitative leap. On one hand, it solves the problem of low power consumption; on the other hand, the problem of direct processing of DC small signal is solved through the use of hybrid analog and digital circuit technology. 

Before we learn operational amplifier,let's see a video before:

In this Video,it explains what Operational Amplifiers (OpAmps) are and how they work. The concepts of negative feedback, open loop gain,

virtual grounds and opamp action. The comparator, the buffer, the inverting and non-inverting amplifiers, the differential amplifier, and the integrator

circuit configurations are also explained.Then a practical breadboard circuit to demonstrate a virtual ground and the effect of voltage rail limitations.

After years of development, analog operational amplifier technology has been very mature, and the performance is perfect with a great variety. This makes beginners do not know how to choose the right one. In order to facilitate the beginners to choose, this article uses two kinds of classification methods such as process classification and function / performance classification to classify the integrated analog operational amplifier, which is easy for the reader to understand and this method may be different from the usual classification methods.

Operational Amplifier--Operational Amplifier Characteristics,Classification,main parameters and types

1.1 Classification based on manufacturing process

According to the manufacturing process, the currently used integrated analog operational amplifier can be divided into standard silicon process operational amplifiers, operational amplifiers incorporating JFET process in a standard silicon process and operational amplifier incorporating MOS process in a standard silicon process . The classification according to the process is to facilitate beginners to understand the influence of the processing technology on the integrated analog operational amplifier performance and quickly grasp the characteristics of the op amp.

  • The characteristics of the integrated analog operational amplifier based on standard silicon process is low open-loop input impedance, low input noise, slightly lower gain, low cost, lower accuracy and higher power consumption. This is due to the fact that the integrated analog op amps of the standard silicon process are all NPN-PNP tube internally. Considering the frequency characteristics, the middle gain stage can not be too much, which will make the total gain smaller, generally between 80 ~ 110dB. The standard silicon process can be combined with laser correction technology to greatly improve the accuracy of integrated analog operational amplifier. The temperature drift parameter can reach 0.15ppm at present. Through changing the standard silicon process, we can design universal operational amplifier and high speed operational amplifier. Typical example is LM324.

  • The operational amplifiers incorporating JFET process in a standard silicon process is mainly improving the input stage of the integrated analog operational amplifier of the standard silicon process to JFET, which greatly improve the open-loop input impedance of the operational amplifier, and the conversion speed of the universal operational amplifier is increased by the way. Other integrated analog operational amplifiers are similar to standard silicon process op-amp. The typical open-loop input impedance is in the order of 1000m ohms. Typical example is TL084.

  • The operational amplifier incorporating MOS process in a standard silicon process are divided into three categories:

  1. (1)The first kind is that the input stage of the integrated analog operational amplifier in standard silicon process is improved to MOS FET, which greatly improves the open-loop input impedance of the operational amplifier compared with the JFET, and increases the conversion speed of the universal operational amplifier. Other integrated analog operational amplifiers are similar to standard silicon process op-amp. The typical open-loop input impedance is in the order of 10 ^ 12 ohms. Typical example is CA3140.

  2. (2)The second kind is an analog operational amplifier using full MOS FET technology, which greatly reduces power consumption, but the power supply voltage is reduced and power consumption is greatly reduced. Its typical open-loop input impedance is in the order of 10 ^ 12 ohms.

  3. (3)The third kind is the analog digital hybrid operational amplifier using full MOS FET technology, which is mainly used to improve the processing accuracy of DC signal by using the chopper stabilization technology. The input offset voltage can reach up to 0.01uV. The temperature drift parameter can reach 0. 02 ppm currently. It is close to ideal operational amplifier characteristics in processing DC signals. Its typical open-loop input impedance is in the order of 10 ^ 12 ohms. Typical example is ICL7650.1.

1.2 Classification based on function / performance

According to functional / performance classification, analog operational amplifiers can be generally divided into universal op amp, low power op amp, precision op amp, high input impedance op amp, high speed op amp, broadband op amp and high voltage op amp. There are also some special operational amplifiers, such as programmable op amps, current op amps, voltage followers and so on. In fact, there are many kinds of operational amplifier in order to meet the needs of application.This article is based on the above simple taxonomy.

That is, with the progress of technology, the classification threshold has been changing. For example, the previous LM108 was originally classified as a precision op amp, and now it can only be classified as a universal op amp. In addition, there are also operational amplifier with low power consumption and high input impedance, or similarly, it may also belong to more than one class.

  • The universal operational amplifiers are the cheapest op amp with the most basic functions. This type of amp is most widely used.

  • The power consumption of low power operational amplifier is greatly reduced on the basis of universal op amp. It can be used in places with limited power consumption, such as handheld devices(PDA). It has low static power consumption and low operating voltage as low as nearly the battery voltage. Also it can maintain a good electrical performance at a low voltage stage. With the development of MOS technology, low power amplifier is no longer an individual phenomenon. The static power consumption of low power op amp is generally less than 1 MW.

  • Precision operational amplifier is an integrated operational amplifier with very low drift and noise and very high gain and common-mode rejection ratio, which is also known as low drift op amp or low noise op amp. The temperature drift of this type of operational amplifier is generally lower than 1uV/℃. Due to technological advances, the offset voltage of early part operational amplifier is relatively high, possibly up to 1 mV; Now the offset voltage of precision operational amplifier can reach 0.1 mV; The offset voltage of precise operational amplifier using chopped stabilization technique can reach 0.005 mV. Precision operational amplifier is mainly used in areas where the precision of amplification processing is required, such as automatic instrument, etc.

  • High input impedance operational amplifier usually refers to the integrated operational amplifier with JFET or MOS tube as input stage. This includes the integrated operational amplifier with full MOS tube. The input impedance of the high input impedance operational amplifier is generally greater than 109 ohms. As a side feature of the high input impedance operational amplifier, the conversion speed is relatively high. High input impedance op amp is widely used. For example, sample hold circuits, integrator, logarithmic amplifiers, [电] instrumentation amplifiers, band pass filters and so on.

  • High speed operational amplifier is an operational amplifier with high conversion speed. Generally, the conversion speed is more than 100V/us. High speed operational amplifier is used in high speed AD/DA converter, high speed filter, high speed sampling hold, phase locked loops, analog multiplier, confidential comparato and video circuit. At present, the highest conversion speed can reach  to 6,000 V/us.

  • Broadband operational amplifier refers to an integrated operational amplifier with a -3dB bandwidth (BW) which is much wider than general op amp. Many high speed operational amplifiers have a wide bandwidth, which can also be called high speed broadband operational amplifier. This classification is relative. The classification of the same op amp under different operating conditions may varies. Broadband operational amplifier are mainly used to process wider bandwidth circuits of input signals.

  • High voltage operational amplifier is designed to meet the requirements of high output voltage or high output power. It is mainly designed to solve the withstand voltage, dynamic range and power consumption problems. The supply voltage of high voltage operational amplifier can be higher than ±20 VDC. the output voltage can be higher than ±20 VDC. 

II.The Main Parameters of Operational Amplifier

operational amplifier characteristics--Operational Amplifier Characteristics,Classification,main parameters and types

There are many parameters of integrated operational amplifier, among which the main parameters are DC parameter and AC parameter.

The main DC parameteres include input offset voltage, input offset temperature drift (referred to input offset voltage drift) , input bias current, input offset current , input offset current temperature drift (referred to as input offset current drift) , differential mode open - loop DC voltage gain , common mode rejection ratio , power supply voltage rejection ratio, peak point voltage of the output, maximum common mode input voltage , and maximum differential mode input voltage .

The main AC parameteres include open loop bandwidth, unity gain bandwidth, conversion rate SRs, full power bandwidth, built-up time, equivalent input noise voltage, differential mode input impedance, common mode input impedance and output impedance.

Let’s take NE5532 as an example.

2.1 DC parameter

Here is the DC electrical characteristics of NE5532:

DC characteristics--Operational Amplifier Characteristics,Classification,main parameters and types

  • Input offset voltage VIO:

The input offset voltage is defined as the compensation voltage between the two input terminals when the output voltage of integrated operational amplifier is zero. The input offset voltage actually reflects the internal circuit symmetry of operational amplifier. The better the symmetry is, the smaller the input offset voltage will be. Input offset voltage is very important to op amps, especially for precision amplifier or DC amplifier. So it is an extremely important parameter for precision operational amplifier.

  • Input offset voltage temperature drift αVIO ( Input offset voltage drift)

The input offset voltage temperature drift is defined as the ratio of input offset voltage change to temperature change within a given temperature range. This parameter is actually a supplement to the input offset voltage. It makes it easy to calculate the drift of amplifier due to temperature change in a given operating range. The input offset voltage of the general operational amplifier is in the range of ±10~20μV/℃. The input offset voltage temperature drift of precision operational amplifier is less than ±1μV/℃.

  • Input bias current IIBS:

The input bias current is defined as the average bias current between the two input terminals when the output DC voltage of the operational amplifier is zero. The input bias current is related to the manufacturing process. The input bias current of the bipolar process (i.e. the standard silicon process mentioned above) is between ±10nA~1μA. The input bias current of amplifier with FET as input stage is generally less than 1nA.

  • Input offset current IIO:

The input offset current is defined as the bias current difference between the two input terminals when the output DC voltage of the amplifier is zero. The input offset current also reflects the symmetry of the internal circuit of the amplifier. The better the symmetry is, the smaller the input offset current will be. Input offset current is very important to op amps, especially for precision amplifier or DC amplifier. 

  • Input offset current temperature drift αVIO ( Input offset current drift)

The input offset current temperature drift is defined as the ratio of input offset current change to temperature change within a given temperature range. This parameter is actually a supplement to the input offset current. It makes it easy to calculate the drift of amplifier due to temperature change in a given operating range. 

  • Maximum common-mode input voltage:

The maximum common-mode input voltage is defined as common-mode input voltage of the op amps when the amplifier operates in a linear region and the common-mode rejection ratio (CMR) is significantly getteing worse. The common mode input voltage is generally defined as the maximum common mode input voltage when the common mode suppression ratio is reduced to 6dB. The maximum common-mode input voltage limits the maximum common-mode input voltage in the input signal. In case of interference, attention should be paid to this problem in circuit design.

  • Common-mode rejection ratio:

Common mode rejection ratio is defined as the ratio of differential mode gain to common mode gain when operational amplifier is in linear region . Common mode rejection ratio is a very important parameter , which can suppress differential mode input. Common mode rejection ratio of normal operation is between 80 and 120 dB .

  • Peak point voltage of the output

The Peak point voltage of the output is defined as the maximum voltage amplitude of the operational amplifier can output when it is supplied by large power supply voltage when the operational amplifier works in the linear region and under the specified load. 

2.2 AC parameter

Here is the AC electrical characteristics of NE5532:

AC characteristics--Operational Amplifier Characteristics,Classification,main parameters and types

  • Open loop bandwidth: 

Open loop bandwidth is defined as the corresponding signal frequency when a small amplitude sinusoidal signal input to the op amp input, measured from the output of the op amp open-loop voltage gain from the op amp's DC gain drop 3db (or equivalent to op amp DC 0.707 gain). This is used in very small signal processing.

  • Unity gain bandwidth GB:

The unit gain bandwidth is defined as the corresponding signal frequency when a small amplitude sinusoidal signal input to the op amp input, measured from the output of the op amp closed-loop voltage gain drop 3db (or equivalent to 0.707 of the operational amplifier input signal). The unity gain bandwidth is a very important indicator. For sinusoidal small signal amplification, the unity gain bandwidth is equal to the product of the input signal frequency and the maximum gain at that frequency. In other words, when knowing the signal frequency and signal to be processed, you can calculate the unity gain bandwidth and select the appropriate op amp. This is for op amp selection in small signal processing.

  • Slew Rate SR:

The slew rate of op amp is defined as the output rate of the amplifier that being measured at the output end of the amplifier when a large signal (including a step signal) is input to the input end of the operational amplifier under the condition that the op amp connected to the closed loop The slew rate is a very important indicator for large signal processing. For general op-amp, the slew rate is SR <= 10V/μs; for high speed op amp, the slew rate is SR> 10V/μs. The current high-speed op amp maximum slew rate SR has reached 6000V/μs. This is used for op amp selection in large signal processing.

  • Full power bandwidth FPBW:

Full-power bandwidth is defined as the range of frequencies in which an op amp operates with full power. This frequency is limited by the op amp slew rate. Approximately, full power bandwidth = SR/ 2πVop (Vop is the peak output amplitude of the op amp). Full power bandwidth is a very important indicator for op amp selection in large signal processing.

3.Op-amp-gain-vs-frequency-chart.png

  • Differential-mode input impedance(input impedence )

Differential mode input impedance (DMI) is defined as the ratio of the voltage variation between the two input terminals and the corresponding input current when the operational amplifier operates in a linear region. The differential mode input impedance includes the input resistance and the input capacitance. At low frequency, it only refers to the input resistance. The general product only gives the input resistance. The input resistance of the operational amplifier using bipolar transistor as the input stage is not more than 10 mega ohms; The input resistance of the field effect transistor (FET) at the input stage is generally greater than 109 ohms.

  • Output impedance

The output impedance is defined as the ratio of this voltage change to the corresponding current change when adding a signal voltage to the output of an operational amplifier working in a linear region. . At low frequency, it only refers to the output resistance of the operational amplifier. 



Analysis

III.Common Operational Amplifier Types

Model(Specification)

Function Introduction

Compatible Model

CA3130

High input impedance operational amplifier

Intersil[DATA]

CA3140

High input impedance operational amplifier


CD4573

Four-programmable operational amplifier

MC14573

ICL7650

Chopped zero stabilized amplifier


LF347(NS[DATA])

Bandwidth-quadruple operational amplifier

KA347

LF351

BI-FET single operational amplifier

(NS[DATA])

LF353

BI-FET dual operational amplifier

(NS[DATA])

LF356

BI-FET single operational amplifier

(NS[DATA])

LF357

BI-FET single operational amplifier

(NS[DATA])

LF398

Sample - and - hold amplifier

(NS[DATA])

LF411

BI-FET single operational amplifier

(NS[DATA])

LF412

BI-FET dual operational amplifier

(NS[DATA])

LM124

Low power four-op amplifier (Military)

(NS[DATA])/ (TI[DATA])

LM1458

Dual operational amplifier

NS[DATA

LM148

Quadruple operational amplifier

NS[DATA

LM2902

Quadruple operational amplifier

(NS[DATA])/

LM2904

Dual operational amplifier

(NS[DATA])/

LM301

Operational amplifier

NS[DATA]

LM308H

Operational amplifier (metal package)

NS[DATA]

LM318

High speed operational amplifier

NS[DATA]

LM358 NS[DATA]

Universal dual operational amplifier

HA17358/LM358P(TI)

LM380

Audio power amplifier

NS[DATA]

LM386-1 NS[DATA]

Audio amplifier

NJM386DUTC386

LM3886

High power audio amplifier

NS[DATA]

LM725

Precision operational amplifier

NS[DATA]

LM733

Bandwidth operational amplifier


LM741 NS[DATA]

Universal operational amplifier

HA17741

MC34119

Low power audio amplifier





Book Recommendation

  • Operational Amplifiers: Theory and Design

This proven textbook guides readers to a thorough understanding of the theory and design of operational amplifiers (OpAmps). The core of the book presents systematically the design of operational amplifiers, classifying them into a periodic system of nine main overall configurations, ranging from one gain stage up to four or more stages. This division enables circuit designers to recognize quickly, understand, and choose optimal configurations.Characterization of operational amplifiers is given by macro models and error matrices, together with measurement techniques for their parameters. Definitions are given for four types of operational amplifiers depending on the grounding of their input and output ports.

--Johan Huijsing (Author)

  • Design with Operational Amplifiers and Analog Integrated Circuits

Franco's "Design with Operational Amplifiers and Analog Integrated Circuits, 3e" is intended for a design-oriented course in applications with operational amplifiers and analog ICs. It also serves as a comprehensive reference for practicing engineers.This new edition includes enhanced pedagogy (additional problems, more in-depth coverage of negative feedback, more effective layout), updated technology (current-feedback and folded-cascode amplifiers, and low-voltage amplifiers), and increased topical coverage (current-feedback amplifiers, switching regulators and phase-locked loops).

--Sergio Franco  (Author)

  • Operational Amplifiers with Linear Integrated Circuits

--William D Stanley (Author)



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