Hello all, I'm trying to apply superposition to the circuit in the figure.

I've found Vo1 and Vo2 and now all that's left to do is determine io.

I've tried to do so in the following manner,

Vo = Vo1 + Vo2,

Then,

\(i_{o} = \frac{V_{o}-V_{L}}{R}\)

But if I were to plug in Vo, the VL will not cancel away, the current Io is supposed to be independent of the load ZL.

However, if I solve for V1 and V2 and use this to create an expression for io in terms of VI it works.

Can someone see what I'm doing wrong?

 

I think perhaps the problem is that both Vo and VL are dependent on the value of ZL. In essence VL lifts Vo by I*ZL.

The obvious way out is to make ZL=0 & hence VL=0.

Then your Vo1+Vo2 approach will work.

 

By the way - did you take the opportunity to read Bob Pease's useful application note on the Howland Current Pump?

I again place the link below for your interest.

http://www.national.com/an/AN/AN-1515.pdf

In my humble opinion, Bob Pease is one of the all-time great electronics guru's.