MosFet Test Problem

121

03:40:45

On the top is an on- off function
but not on the lower. Why?

published 10 years ago

hurz

10 years ago

Because gate outputs are like ideal voltage source with zero impedance!

nikisalli

10 years ago

The logic gate charges and discharges the "capacitor" of the mosfet because the logic gates provides 5v and 0v in the other case it only charges the "capacitor" and the mosfet remains high

pickels

10 years ago

Thanks! :)

Zheka10011

10 years ago

Open on a logic gate stays high, while the lower one has somewhere to ground.

zorgrian

10 years ago

Needs a path to ground from the gate but no need for such low impedance. 1-10 meg resistor might be reasonable

zorgrian

10 years ago

Also 'the lower fet' does function as an 'on off ' circuit. And I've just refreshed the app to see that the comment I would have inserted about gate capacitance has already been stated.

zorgrian

10 years ago

Hurz, do you say that a real mosfet gate behaves as an ideal voltage source with zero impedance '?

zorgrian

10 years ago

I'm guessing you mean in the EC world?

hurz

10 years ago

I said "gate" i mean "logic gate"!!!! Anyway, i also talked about an output and thought its clear.

zleeping

10 years ago

The logic has constant voltage supplying the gate.

zleeping

10 years ago

The top saturates the gate opening it then u sink voltage through resistor closing gate. Bottom constant voltage from logic source cannot sink through resistor.

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