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Op-amp understanding related to inverting Amplifier

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Bjtpower

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Hello Friends.

I am having a -0.5V Signal which i need to be inverted with the OP-AMP of supplying +5V w.r.t to GND (No negative supply is going to be connected)

Does it amplify..??

If Yes, Then which Parameter of datasheet i should have to look for..??

Regards
Marx
 

srizbf

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Hello Friends.

I am having a -0.5V Signal which i need to be inverted with the OP-AMP of supplying +5V w.r.t to GND (No negative supply is going to be connected)

Does it amplify..??

If Yes, Then which Parameter of datasheet i should have to look for..??

Regards
Marx

Can you explain your requirement ?
 

Bjtpower

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Hi...

I want to amplify the shunt signal which is negative in nature (Amplitude->Max -500mV)

Power Supply=+5V and GND for OP-AMP

Inverting: Because the signal will get inverted with gain of 1-2

That signal will then apply to another stage..
 

srizbf

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Single supply opamps like LMx24 series is suitable.
There are many others of the same category.

Gian of 1-2 is not a problem.

The shunt voltage is to be capacitor coupled with opamp input.
 

KlausST

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Hi,

As an experienced edaboard use you know: A picture/schematic says more than thousand words.
A textual description of a circuit is always vague....and the same vague are our answers.

Besides a circuit.. we need to know your signal specification:
* What frequency
* what waveform
* and what else is important for you
* do you need DC stability?
* do you
* also: what do you do with the signal? ADC? comparator?

And you need to describe the desired output.
* especially precision
* allowed offset voltage
* allowed noise
* expected precision

***
As far as I understand..Your OPAMP requirements are:
* Input common mode voltage needs to include GND rail.
* Output needs to go close to GND rail. --> look for rail to rail output OPAMP
* GBW: I recommend at least 5 x highest_input_signal_frequecy_of_interest (mind that any non sinusoidal waveform has overtones, that you need to take care of)
* slew rate: unknown for us --> decide on your own
* stable with gain of +2

* My recommendation: Shift the output signal some +10mV DC above GND level, to safely keep the OPAMP in regulation state. Best is to do this with a small offset at the +In input.

Klaus
 

Bjtpower

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Here i am attaching he image of the LYTSWITCH.
The FB Pin voltage is not exceeds -280mV W.R.T TO Source.

The above circuit is working fine.

Now, if i am removing wire from the FB Pin and connecting to the Op-amp negative terminal or By keeping the FB PIN and only wire taking for the SIgnal Measurements the output gets Fluctuates.

Red part i want to amplify with opamp with variable gain so i can change the Current as well.

For reference,
https://www.google.co.in/search?q=d...rome..69i57.2591j0j7&sourceid=chrome&ie=UTF-8

lytswitch.jpg
 

KlausST

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Hi,

I´ve already told you my solution to this problem. But I´ve got no feedback from you why you don´t want to use it.

****
Your solution is way more complicated. Not only because it needs more parts...but additionally it may harm LUT function completely.
I personally don´t know how exactely the feedback of the LUT works.
(But if you want to design a circuit for the LUT then you should know this)
If the feedback is part of a cycle-by-cycle current limiting ciruit, then the OPAMP response needs to be fast enough not to introduce phase shift or overshoot.
With the high swtching frequency of the LUT this may become challenging.

No way to use a slow OPAMP like LMx24.

Good luck

Klaus
 

Bjtpower

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Hi,
FB Pin is cycle by cycle controlled.
The FB Pin voltage is -279mv w.r.t to Source.

Now with the inverting Amplifier having a gain of 2 will give +279mv*2=560mV
Now fb pin will want the -560mv How we can do it with the single supply (+5v and GND)

Another thing is that,
In single supply opamp

What input voltage will aply to the Inverting/Non-inverting Pins (Range)->Where in datasheet is expressed..??

Here i am attaching the Waveform of Source w.r.t to the FB PIN which is 78khz signal and Amplitude max -279mV
TEK0003.JPG

Marx
 

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