Diferent Op-Amps

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Iodem_Asakura

Joined Sep 14, 2004
140
Are there diferent Op-Amps? Someone told me that some Op-Amp ICs only works as comparators, so can't be used like inverter amplifiers (ex. LM339). Is that true?

So are there Op-Amps that can be used only in some configurations and not in others?
 

hgmjr

Joined Jan 28, 2005
9,029
Originally posted by Iodem_Asakura@Jun 26 2005, 01:11 AM
Are there diferent Op-Amps? Someone told me that some Op-Amp ICs only works as comparators, so can't be used like inverter amplifiers (ex. LM339). Is that true?

So are there Op-Amps that can be used only in some configurations and not in others?
[post=8731]Quoted post[/post]​
iodem_asakura,

Are there diferent Op-Amps?
Yes, There are two types of operational amplifiers available to the electronic circuit designer. One is the classical operational amplifier whose output is a voltage that is proportional to the difference between the voltages applied to its positive and negative inputs. The second type of operational amplifier goes by the name operational transconductance amplifier or OTA for short. For the OTA, the output is a current that is proportional to the difference between the voltages applied to its positive and negative input terminals.

All operational amplifiers can be used in the various gain configurations (inverting, non-inverting, etc.)

There is another type of device that shares the same schematic symbol as the operational amplifier. This device is a voltage comparator. The LM339 is this type of device. The voltage comparator is a classical op-amp on steroids. Its gain has been deliberately designed to be as high as possible so that just the least difference between its positive and negative input will drive the output voltage to its maximum output voltage in the positive or negative direction. This high gain comes at a price. The high gain involves more gain producing stages inside the device. These additional gain stages introduce a delay between the voltage change at the input and the corresponding voltage change at the output. This delay makes the voltage comparator unsuitable for use as an operational amplifier.

Although you cannot use an voltage comparator as an op-amp, there is nothing to prevent the use of an op-amp as a voltage comparator.

I hope this explanation is helpful.

hgmjr
 

hgmjr

Joined Jan 28, 2005
9,029
Originally posted by Iodem_Asakura@Jun 26 2005, 07:34 AM
Yes, that was a great explanation.

How can i identify each one by the datasheet?
[post=8736]Quoted post[/post]​
The datasheet should clearly identify the type of device in its title.

hgmjr
 
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