A voltage divider in terms of a conductance

[bitrex]

I am looking at the following application note that goes into nodal analysis of op amps: http://www.maxim-ic.com/appnotes.cfm/an_pk/1939/ and down at the bottom where they're analyzing the Wien bridge oscillator the equation at the negative input of the op-amp taken from the output in terms of conductance is Gf/(Gi+Gf). I'm not sure how they got that - if expressed in terms of resistances that voltage divider is Ri/(Rf+Ri). How does one change the equation for a voltage divider in terms of resistance to terms of conductance?

 

[The Electrician]

I am looking at the following application note that goes into nodal analysis of op amps: http://www.maxim-ic.com/appnotes.cfm/an_pk/1939/ and down at the bottom where they're analyzing the Wien bridge oscillator the equation at the negative input of the op-amp taken from the output in terms of conductance is Gf/(Gi+Gf). I'm not sure how they got that - if expressed in terms of resistances that voltage divider is Ri/(Rf+Ri). How does one change the equation for a voltage divider in terms of resistance to terms of conductance?

In this expression, Ri/(Rf+Ri), substitute:

1/Gf for Rf
1/Gi for Ri

then simplify and you should get the voltage divider formula in terms of conductance.