[SOLVED] Op-Amp Positive Supply drops down..........

[SACHIN C]

Dear All,

Pls help me out,Whenever i am connecting Sinewave(5Vp-p\50Hz) generated using XR2206 to TL074 Non-Inverting Terminal used as an difference op-amp,the voltage of sinewave gets reduced to 1.68Vp-p & simultaneously Op-Amp +15 V drops to 4.68V.

I have connected +15 V & -15 V to the Op-amp :smile:

Is 680E connected for current limit affects?
or
XR2206 is not capable to deliver the amount of current required by the TL074?

 

[keith1200rs]

Is 680E connected for current limit affects?

What 680E? I think you need to post your circuit!

Keith

 

[SACHIN C]

680E is the value of resistor connected for TL074 op amp current restriction.........

 

[keith1200rs]

That still doesn't make any sense. Post your schematic.

Keith

 

[SACHIN C]

Dear All,
Pls help me out can we apply +15V & -15V to TL074 opamp & 741 Op-Amp as an supply voltage?:!:
If yes than what should be the Limiting resistor like TL074 needs 1.6mA per Amplifier?:smile:

Thanks.....

 

[kam1787]

post the circuit

 

[SACHIN C]

Pls find the attached file for circuit.....
XR2206 used two :for Triangular & Sinewave Generation but,in circuit shown single.


Thanks & Waiting for valuable help......:smile:

 

[keith1200rs]

Where is the 680 ohm resistor you keep talking about? I cannot see it.

Keith

 

[tpetar]

Who knows what circuit we are looking.

 

[SACHIN C]

keith
680 ohm resistor connected for current limit in between 7815 & opamp +15v......
I am confused with opamp power supply because i have used +15v & -15V supply for Op-Amp is it fine or exceeds opamp max.?

Thanks......:smile:

 

[keith1200rs]

The TL074 can run up to 36V total supply so +/-15V is fine. You should NOT put resistors in the supply line! Sometimes this might be done with a small resistor and decoupling capacitor after it but otherwise you are simply going to end up with a circuit which doesn't work.

The resistor values in your circuit seem rather low. I haven't checked in detail but the opamp may struggle with such low values.

Keith

 

[SACHIN C]

Keith
so i didn't need to connect current limiting resistor for opamp?
Also i used 741 opamp to generate 3.5Vp-p Sinewave with same suppl +15V & -15V is that fine?
IS XR2206 capable to deliver the Tl074 required current (XR2206 Sinewave Output connected to TL074 Pin 3 & Pin 10 Non-Inverting)?
At 1st stage the difference must be obtained at the pin 1,but it is variable upto 7Vp-p(Pin 2 Inverting Sinewave 3.5Vp-p & Pin 3 non-Inverting Sinewave 5.10Vp-p)?
Also XR2206 output connected to buffer and then buffer output to opamp(Pin 3) still not working,the positive cycle of sinewave at output varies in amplitude?


thanks.....:smile:

 

[keith1200rs]

As I said, you rarely put resistors in opamp power supplies and not for current limiting anyway - only for removing high frequency noise coupling.

741 is fine on +/-15V. I think you need to increase the resistor values. I wouldn't normally be using less than 2k ohms anywhere on a circuit like that, using TL074s which have a JFET input. 22k and 220k would be typical resistors you might be using. The opamps will not be able to drive large voltage swings into the low value resistors.

Keith

 

[SACHIN C]

Keith
Thanks for explaining the resistor function in between Op-amp and power supply....:smile:
How can a resistor only isolate high frequency noise or as you said we need to use cap also in that situation?
Surely i will revert back after changing the resistor as 22ohm by 22k & 220ohm by 220k

Thanks.....:smile:

- - - Updated - - -

After replacing 22ohm by 22k & 220ohm by 220K the positive signal trip problem solved but, the stage wise output is not proper?
Pls suggest me the proper resistor required for the above attach circuit????:!:


thanks.......

- - - Updated - - -

After replacing 22ohm by 22k & 220ohm by 220K the positive signal trip problem solved but, the stage wise output is not proper?
Pls suggest me the proper resistor required for the above attach circuit????


thanks.......

 

[SACHIN C]

Dear all,
What will happen if i replace Ground by negative supply ground for above attached circuit???????:!:


Thanks:smile:

 

[kam1787]

Dear all,
What will happen if i replace Ground by negative supply ground for above attached circuit???????:!:

Why do that?

 

[SACHIN C]

Kam1787,
Using single supply for Op-Amp,it causes level shift of Sinewave with 3.58vdc above X-axis .
So,i thought using dual supply which can give us DC shift above & below X-Axis,so that it can be feed to the Comparator.:?:

Thanks,:smile:

 

[kam1787]

Do you mean truncation (and not level shifting)?

I think you had meant to say in the prior post , "What will happen if I INCLUDE Ground (with +- voltage supply) for above attached circuit?"

You had stated, "I have connected +15 V & -15 V to the Op-amp" so I had presumed it was +15V, Ground, and -15V


Normally connecting a dual power supply assumes the use of Ground. Otherwise we would say it is a [single-ended] power supply of 30V.

 

[SACHIN C]

Kam1787,
Actually I powered Opamp with +-15V but,Sinewave generated Using XR2206 With +15V & Ground so the Sinewave is with respect to ground is lifted?

Thanks,:smile:

 

[kam1787]

not lifted. it is TRUNCATED