Operational Amplifier

[Anusha_dhananjaya]

HI ;-)
I was going through op-amp.... I have certain doubts.....
1) Concept of virtual ground
2) Output swing
can anybody please answer this..... thanks a lot in advance :smile:

 

[rongo024]

read two books. Microelectronics and CMOS by Razavi

 

[Anusha_dhananjaya]

Thanks a lot... I am a beginner.. Op amp is in my syllabus..... I will consider ur advise thanks

 

[Chipmunk]

You can donwload a book from Texas Instruments for free that is quite good: Op Amps for Everyone by Ron Mancini

**broken link removed**

Please have a look at sections
3.3 The Inverting Op Amp (contains a short explanation of virtual ground) and
11.3.5 Maximum Output Voltage Swing

 

[SABIRALI]

Read some simple texts first....

 

[sadmax]

I/p impedance of an opamp is very high and hence very little current flows thru it's inputs and hence very little voltage drop occurs at i/p.Hence if one of it's i/p is grounded ,since voltage difference b/w two i/ps will be very less we can assume other one of the i/p also to be at ground and hence giving rise o term 'virtual gound'.

 

[LvW]

I/p impedance of an opamp is very high and hence very little current flows thru it's inputs and hence very little voltage drop occurs at i/p.Hence if one of it's i/p is grounded ,since voltage difference b/w two i/ps will be very less we can assume other one of the i/p also to be at ground and hence giving rise o term 'virtual gound'.

The high input impedance of the opamp inputs is NOT the reason for the "virtual ground concept". Remember: This concept applies also to the Current-feedback topology with a very low negative input impedance.
The background is the very high loop gain that very often can be assumed to approach infinity.