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DC Models

According to equation (110) the JFET acts like a nonlinear voltage controlled current source when operating in its active region. This leads to the DC equivalent circuit shown in Figure 127.

  

Figure 127: JFET DC equivalent circuit.

Note that G-S is shown as an open circuit, and so in this model I_G=0. The current I_D=I_S is then given by the nonlinear current source.

This model is also used for D MOSFETs. For E MOSFETS, we replace $I_{DSS}(1- \frac{v_{GS}}{V_p} )^2$ with K( V_GS - V_GS(th) )².

The DC model is only valid when the transistor is operating in its active region.

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