Operational+Amplifiers

toc = Introduction = Operational Amplifiers often known as Op-Amps are used in a range of circuits. They are generally used to amplify weak electrical current in a circuit. It is one of the most versatile devices in all of electronics. Op-amps are integrated circuits that cram the equivalent of many transistors, resistors and capacitor into a small silicon chip. It is not important to know what the circuit looks like but to understand the functions the Operational Amplifiers can perform. The most popular type of **Op Amp** is the **741** as shown below as 8 pin dual layout IC's. They are represented in circuit diagrams as follows:
 * Operational Amplifiers** are** voltage amplifiers **, and transistors are current amplifiers
 * [[image:http://upload.wikimedia.org/wikipedia/commons/thumb/0/0b/Op-amps.jpg/350px-Op-amps.jpg width="280" height="156"]] ||  || [[image:http://upload.wikimedia.org/wikipedia/commons/thumb/9/97/Op-amp_symbol.svg/150px-Op-amp_symbol.svg.png align="center"]] ||   || ** //V// + : non-inverting input**


 * //V// − : inverting input**


 * //V//out : output**


 * //V////S// + : positive power supply**

The op-amp is basically a differential amplifier having a large voltage gain, very high input impedance and low output impedance. The op-amp has a "inverting" or (-) input and "non-inverting" or (+) input and a single output. The op-amp is usually powered by a dual polarity power supply in the range of +/- 5 volts to +/- 15 volts. = Uses = Operational Amplifiers are used in a range of circuits:
 * //V////S// − : negative power supply** ||
 * as an operational amplifier
 * as a comparitor

They are generally used to **amplify** weak electrical current in a circuit. For example: And many other electrical products need operational amplifiers in order for them to work properly, when using sensors as an input (switch) it is often necessary to increase **(amplify)** the current in the circuit For example The most common Op-Amp is the 741 and it is used in many circuits. For example, a temperature sensor may to used to detect fire and then to turn on a water sprinkler system to put the fire out. Look at the animated example from [|www.technologystudent.com] below: media type="custom" key="3517752" When the rise in temperature (caused by the fire) is detected the sensor circuit (including an operational amplifier) allows a small amount of current to flow through it. However, the current is too small to activate the sprinkler system. The current must be increased for this to happen. An operational amplifier is used to increase the current (called GAIN). Then the sprinkler system is turned on putting out the fire. media type="custom" key="3517764"
 * Radios
 * Stereo systems
 * Headphones
 * Televisions
 * Moisture sensors
 * Light / dark sensors
 * Movement sensors
 * Sound sensors often

= Function = The important pins of the 741 are: The chip can be used in a circuit in two ways. If the voltage goes into pin 2 then it is known as an **INVERTING AMPLIFIER**. If the voltage goes into pin 3 then the circuit becomes a **NON-INVERTING AMPLIFIER**.
 * 2 - inverting
 * 3 - non-inverting
 * 6 - voltage out

How does an operational amplifier work?

In an inverting amplifier the voltage enters the 741 chip through leg two and comes out of the 741 chip at leg six. If the polarity is positive going into the chip, it negative by the time it comes out through leg six. The polarity has been ‘inverted’. Here is video using a different operational amplifier the LM 324 media type="custom" key="7600263" In a non-inverting amplifier the voltage enters the 741 chip through leg three and leaves the 741 chip through leg six. This time if it is positive going into the 741 then it is still positive coming out. Polarity remains the same. = Calculations = @http://www.technologystudent.com/elec1/opamp2.htm @http://www.petervis.co.cc/calculators/opamp/opamp.html Voltage dividers: @http://www.raltron.com/cust/tools/voltage_divider.asp
 * 1. An inverting amplifier.** Leg two is the input and the output is always reversed.
 * 2. A non-inverting amplifier.** Leg three is the input and the output is not reversed.
 * Calculators**

= History = Vacuum Op-Amp [] [|http://www.uoguelph.ca/~antoon/gadgets/741/741.html] [] []
 * Links**

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