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Op Amps-Operational Amplifiers

2015-01-01 04:27  
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Introduction to Operational Amplifiers

Basic Op-Amp Circuit

Basic Op-Amp Circuit

An operational amplifier, abbreviated as op-amp, is basically a multi-stage, very high gain (typically 2,00,000), direct-coupled, negative feedback amplifier that uses voltage-shunt feedback to provide a stabilized voltage gain. An op-amp has high input impedance (ex-ceeding 100 kilo Ohms) and low output impedance (less than 100 Ohms) and has capability of ampli-fying signals having frequency ranging from zero Hz to 1 MHz, that is, op-amp can be used to amplify dc as well as ac input signals. Although discrete op-amps are built, designers of industrial electronic circuit now useintegrated circuitoperationalamplifiers(IC op-amps) almost exclusively. They are made with different internal configurations in linear ICs. An op-amp is so named as it was originally designed to perform mathematical operations such as summation, subtraction, multiplication, differentiation and integration etc. Now-a-days, the op-amps are put to a variety of other uses such as sign changing, scale changing, phase shifting, voltage regulation, analog computer operations, in instrumentation and control systems, oscillator circuits, pulse generators, square-wave generators, triangular-wave generators, comparators, analog to digital and digital to analog converters (ADC and DAC); voltage-to-current converters, current-to-voltage converters, sample-and-hold cir-cuits etc.

The op-amp manufactured with integrated transistors, diodes, resistors and capacitors, is an extremely versatile device that is found doing countless tasks, as enumerated above and many more. The op-amp is a complete amplifier having the advantages of an IC such as low cost, small size, high reliability, temperature stability and low value of offset voltage and current. Furthermore, it is designed in such a way that external components like resistors, capacitors etc. can be connected to its terminals and external characteristics can be changed. Various amplifier characteristics can be tailored to fit a particular application merely by changing a few components, without redesigning the entire amplifier. This is because the voltage gain, input impedance, output impedance, and frequency bandwidth depend almost solely on stable external resistors and capacitors. The voltage gains of IC op-amps are extremely large, typically 2,0,000. Because of this large voltage gain, externally connected resistors must be employed to provide negative feedback for most of the applications.

A basic introduction of uA741 op-amp has already been given. Check out the link below.

?Introduction to uA 741 Op-Amp

The article mainly describes what an op-amp is., the op-amp symbol, the concept of the inverting and non-inverting input, and many more. It also describes about the popularity of th 741 IC, among th different types of op-amps available in the market. The op-amp features, and the need for dual power supply for the IC is also explained . You can understand more about the packaging style, and the op-amp pin assignment along with the different ratings of an ideal op-amp 741 IC. Some of the basic applications of an op-amp are listed below. Check out the detailed description by clicking on the main links.

Op-amp Comparator

The circuit diagram and the working of an op-amp as a comparator are shown in the article. There are mainly two types of comparators. One is the inverting comparator circuit, and the other is the non-inverting comparator. Both of them are explained with neat waveforms, and the different applications of the circuit are also given.

Schmitt Trigger Using Op-amp

The application of op-amp as a fast operating voltage level detector is shown in this main article with the help of a circuit diagram and its corresponding waveform. The exact working of the circuit is also explained with the equations of the different reference voltages when the output is positively saturated and negatively saturated. The different characteristics of the schmitt trigger is also explained along with its UTP and LTP.

Astable Multivibrator Using Op-amp

The working of op-amp as a square wave generator is explained with the help of a circuit diagram and waveform. The output voltage equation, and the capacitor charging equation is also given. The reason for calling the circuit a “free-running multivibrator” is also explained.

Monostable Multivibrator

The basics of pulse generator is explained in this post. The circuit diagram and waveform is illustrated in the article along with the steady state conditions and capacitor voltage equations.

Zero Crossing Detector

This is an applied form of an op-amp comparator circuit. Here the reference voltage is made zero. The zero crossing detector using inverting op-amp comparator is explained with a circuit diagram and waveform.

Voltage Splitter Using Op-amp

A voltage divider circuit is connected to the non-inverting input of an op-amp. The circuit is explained in detail in the original post.

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