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# Sallen and Key Nodal Equations

#### Chr1s

Dec 20, 2016
27
Can anyone help me with this problem? i am not quite sure where to start?

Thanks

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#### Harald Kapp

##### Moderator
Moderator
Nov 17, 2011
13,828
i am not quite sure where to start?
Start by labeling the voltages across the components with unique labels (V1, V2, V3, ...).
Use complex impedances (frequency dependent) for the capacitors - you should know how to express those.
Use Kirchhoff's voltage law to set up equations for the mesh voltages.
Transform the resulting equations to match the standard form.

As a prerequisite assume an ideal operational amplifier with infinite input impedance (equivalent to Iinput = 0 A) and infinite gain (equivalent to V(in_+) - V(in_-) = 0V)

#### LvW

Apr 12, 2014
604
Everything OK with Haralds answer.
Nevertheless, according to my experience it is more easy to use Kirchhoffs current law for each oif the various nodes (using the voltages between each node and ground).

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