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JFET Voltage divider bias circuit

For the circuit above how is this formula for I(D) derived, a V(D) of 7v was given in the question?

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i know that IS=ID how come RD is being used in the foRmula and not RS?

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  • \$\begingroup\$ Because Ohm's Law? \$\endgroup\$
    – DSWG
    Sep 7, 2018 at 1:06

2 Answers 2

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jfet

formula

I(S) = [V(S) - 0]/R(S). V(S) is not stated so cant use R(S) to find I(S) or I(D).

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Because the calculation is just to find the voltage across RD and from there the drain current. We don't know the voltage across RS so that cannot be used.

Once you have the drain current you can then calculate the voltage across RS. (7*2.2/3.3) = 4.66V.

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