What is a Summing Amplifier and how does it work?

[ally34]

Homework Statement

Please refer to attached image!

Homework Equations

Absolutely no idea how to start this problem!

The Attempt at a Solution

A) I would think that there are 4 input combinations for this circuit.

B) 0110 = 6v?

C) No clue

D) 1011 = 11v?

E) No clue

 

[likephysics]

Part C is simple, the input is given in sin(2*pi*f*t). Just plug n chug to find f.

 

[ally34]

Part C is simple, the input is given in sin(2*pi*f*t). Just plug n chug to find f.

How is the input given in sin(2*pi*f*t)??

 

[likephysics]

How is the input given in sin(2*pi*f*t)??

It's a standard way of writing AC voltage or current, sin(2∏ft) or sin(ωt), cos (ωt)
I don't really know why it is this way.

 

[ally34]

It's a standard way of writing AC voltage or current, sin(2∏ft) or sin(ωt), cos (ωt)
I don't really know why it is this way.

But the problem vs(t) = sin(4000pit)

So ω = 4000?

2pi*f*t = 4000*pi*t

so f = 2000hz?

 

[likephysics]

But the problem vs(t) = sin(4000pit)

So ω = 4000?

2pi*f*t = 4000*pi*t

so f = 2000hz?

Yup.

 

[ally34]

Yup.

Cool -thanks.

How about Part D?

 

[likephysics]

It's a summing amplifier. When one input is grounded, contribution from that branch is zero.
For the other inputs, since 3 resistors are connected to same voltage, they are in parallel.
This should help you understand summing amplifiers - http://www.ecircuitcenter.com/circuits/opsum/opsum.htm