Discussion in 'Homework Help' started by dakanat, Dec 1, 2008.

1. ### dakanat Thread Starter Member

Nov 12, 2008
25
0
hi all

we have gain and offset circuit so,
I used this circuit summing and inverting amp

can you help me to discussion this circuit carefully

2. ### beenthere Retired Moderator

Apr 20, 2004
15,808
295
Last edited: Dec 1, 2008
3. ### beenthere Retired Moderator

Apr 20, 2004
15,808
295
Your first stage gives an amplification of 10. The second amplifies by 2.67. The DC current through the 10K resistor will offset the signal (whatever it is) by an amount equal to 10 times the DC current. Overall performance will depend on the op amp used and if the supply is bipolar.

It would be better to post the circuit into this thread if you wish more people to see it.

4. ### dakanat Thread Starter Member

Nov 12, 2008
25
0
i am jest need conlusion for this circuit:

for :- Technical conclusion & Learning conclusion

thanks

5. ### steveb Senior Member

Jul 3, 2008
2,431
469
Can you be more specific. Are you looking for help in terms of verbal discussion or mathematical analysis?

Some basic things are that the first stage is an inverting amplifier with a gain of 10 according to the schematic. Although, the reference VR1 suggests that that resistor (and hence gain) is variable. The second stage is an inverting amplifier with a gain of 2. Again, the schematic shows a fixed resistor and gain, but the reference VR suggests a variable resistor. The second stage is configured as an inverting adder which allows an offset voltage (DC) to be added to the output. The use of the reference DC suggests that this is intended for DC offset compensation, or (more likely based on the values) just level shifting.

One interesting thing is that the second stage uses all 75k resistors and uses two in parallel. This is a trick to get very good accuracy. Typically resistors have a certain tolerance (1% or 5% probably the most common today). However, if you buy a reel of resistors for production, they tend to be closely matched to each other to much higher accuracy. Since OPAMP gains are a ratio of resistances, the gains of the circuits can be much more accurate than the tolerance would suggest.

Last edited: Dec 7, 2008
6. ### dakanat Thread Starter Member

Nov 12, 2008
25
0
Thanks
So, Are you agree with it or not.

7. ### steveb Senior Member

Jul 3, 2008
2,431
469
I'm not sure what you mean. If you are asking whether I agree that you have presented a circuit that provides both gain and offset, then yes, I agree.

8. ### Papabravo Expert

Feb 24, 2006
12,290
2,728
What are we agreeing with? Are you asking does the circuit have gain? Yes I think it does. Does the output have an offset control? Yes I think it does. Are you going to get a good grade on this assignment? Ahh...I dunno since you did not say anything about the requirements.