Linear Combination OP Amp Design

[TBarlow]

So, I have about 8 questions along the same lines as this, and what I am looking for is any kind of formula's to assist in how to figure this problem. The problem is as follows:

Design a linear combination circuit to combine three signals as follows:

Vo = -2v(sub)1 - 8v(s)2 - v(s)3

The following specifications are imposed:
a. Rin (Greater or equal to) 20kΩ at all inputs
b. all resistance values (smaller or equal to) 200kΩ

I've been beating my head against the wall trying to figure out where to get started, and or how i can calculate this. Any help would be greatly Appreciated

 

[Martaine2005]

I don't think you have been banging hard enough....
Have a little catch up here

All jokes aside. I feel your pain.
May be this should have been posted in the Homework section.
Martin

 

[davenn]

indeed ... it is moved

 

[Ratch]

So, I have about 8 questions along the same lines as this, and what I am looking for is any kind of formula's to assist in how to figure this problem. The problem is as follows:

Design a linear combination circuit to combine three signals as follows:

Vo = -2v(sub)1 - 8v(s)2 - v(s)3

The following specifications are imposed:
a. Rin (Greater or equal to) 20kΩ at all inputs
b. all resistance values (smaller or equal to) 200kΩ

I've been beating my head against the wall trying to figure out where to get started, and or how i can calculate this. Any help would be greatly Appreciated

I think an operational amplifier summer is in your future. See if this link gets you started. http://electronicdesign.com/ideas-design/efficiently-design-op-amp-summer-circuit

Ratch