DC Feed

A DC feed is an inductor with an infinite inductance. The MNA matrix entries of a DC feed correspond to an ideal short circuit during DC analysis:

$$\begin{bmatrix}. & . & +1\\ . & . & -1\\ +1 & -1 & 0\\ \end{bmatr... ...in{bmatrix}I_1\\ I_2\\ 0 \end{bmatrix} = \begin{bmatrix}0\\ 0\\ 0 \end{bmatrix}$$ (9.19)

During AC simulation the DC feed is an open circuit. Thus, its MNA entries are all zero.

The scattering parameters writes as follows.

$$(S) = \begin{pmatrix}1 & 0\\ 0 & 1\\ \end{pmatrix}$$ (9.20)

A DC feed is noise free. A model for transient simulation does not exist. It is common practice to model it as an inductor with finite inductance whose value is entered by the user.