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Earthing the feedback loop in voltage follower

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sayurabh

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in volatge follower circuit using opamp i short the feedback loop but what happens if i earth the feedback loop for eg in non inverint amplifier voltage follower if earthed the negative terminal what hppens to the output it remains same as input tothe positive terminal or not suggest me
 

Re: voltage follower

At noninverting amp, it is not very smart to connect V- to gnd, because you will not get what you want...

33_1179695734.jpg


As you can see Vout=0...

Even if you add resistor you will not get what you want... As feedback is applied, V+ must be equal to V-, but as you see it is not, because V- is gnd...
38_1179695814.jpg



So the best way is useing inverting amp....


If you need to use noninverting best way is to select resistances so that R1>>R2...
A = (1+R2/R1) => A=1 if R2/R1=0 => R1>>R2
93_1179696390.jpg
 

voltage follower

If you earth the inverting input (V-) of the opamp, then this voltage follower becomes a simple comparator. Then if input on non-inverting pin (V+) is > 0V then ouput (Vo) is +V ie max pos supply voltage - saturation voltage of the output stage. Similarly if input on V+ is < 0V then output is -V ie negative supply voltage (- saturation voltage, of couse).
 

Re: voltage follower

You are right if there is no feedback... But without feedback you cannot get voltage folower, cause it is always behaveing as comparator
 

Re: voltage follower

sayurabh,
If you "Earth" the inverting input, you no longer have negative feedback. You now have an amplifier whose voltage gain is the same as the open loop gain of the op-amp.
Regards,
Kral
 

Re: voltage follower

sayurabh said:
in volatge follower circuit using opamp i short the feedback loop but what happens if i earth the feedback loop for eg in non inverint amplifier voltage follower if earthed the negative terminal what hppens to the output it remains same as input tothe positive terminal or not suggest me
Click to expand...
woh it is crystal clear that ur o/p is shorted to ground .
 

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