Why input impedance of mosfet is high?
So as opposed to a BJT transistor (which has a large but measurable input impedance) a Mosfet has even larger (presumably infinite) impedance. The reason is because of a small non-conducting zone that exists between the Gate side and the Drain-Source side. It acts as a small capacitor (which capacitors have infinite resistance), and the electromagnet field produced is what drives current between Source and Drain.
Now, why is this desirable? In the case of BJT's there is a small current that flows into the base, essentially drawing small but existent power from the circuit connected at the Base. It is more ideal to have a transistor that completely separates the current of the control circuit and the current in the circuit being switched/supplied.
Simply, it means its more efficient. When BJT transistors are turned off, power is still being used. The same isn't necessarily true for Mosfet transistors.
Join Date 7-123 Location Some Where In Heaven Posts 415 Helped 91 / 91 Points 7,314Level 20 fet high input impedance The gate lies on an insulated thin oxide layer (dielectric) above the substrate between the source and drain. The gate is effectively one side of a capacitor. This is the input impedance being referred to - the fact that the gate has no DC path to either source, drain or substrate.
Join Date Sep 2006 Posts 189 Helped 9 / 9 Points 2,445Level 11 mosfet input impedance Originally Posted by Awarapunshee The gate lies on an insulated thin oxide layer (dielectric) above the substrate between the source and drain. The gate is effectively one side of a capacitor. This is the input impedance being referred to - the fact that the gate has no DC path to either source, drain or substrate.
Thanks for the reply but I am still a bit confused. Can you please show it pictorically? Join Date 17-12-087 Location Asia Posts 247 Helped 31 / 31 Points 3,046Level 12 why is the input impedence to a jfet so high?
Join Date 17-12-088 Location Bangalore,India Posts 207 Helped 35 / 35 Points 2,684Level 12 fet input impedance yes. In case of BJT the input impedence is between emmiter and base and the junction is forward biased. Had the base been highly doped, the input impedence wiuld have been very low.
With light doping in the base this impedance is increased. Join Date 17-12-089 Posts 16 Helped 1 / 1 Points 1,022Level 7 why is the input impedance to a jfet so high? In jfet the gate-channel junction is always reverse biased so the input impedance is high.
If it was forward biased the input impedance bocomes very low. Join Date 7-123 Location indore Posts 2 Helped 0 / 0 Points 466Level 4 why is the input impedance of JFET and MOSFET very high? You mean 'common emitter configuration?
Join Date 7-123 Posts 95 Helped 5 / 5 Points 1,367Level 8 Re: why is the input impedance of JFET and MOSFET very high Used in BJT...what? Join Date 7-128 Location pakistan Posts 60 Helped 0 / 0 Points 480Level 4 Re: why is the input impedance to a jfet so high? Originally Posted by sasaberali in jfet the gate-channel junction is always reverse biased so the input impedance is high.
If it was forward biased the input impedance bocomes very low. Gate to channel junction ....? Do you mean gate to drain junction by this...?
I cant really gove you an answer,but what I can give you is a way to a solution, that is you have to find the anglde that you relate to or peaks your interest. A good paper is one that people get drawn into because it reaches them ln some way.As for me WW11 to me, I think of the holocaust and the effect it had on the survivors, their families and those who stood by and did nothing until it was too late.
Related Questions
Why do you need high input impedance?
Sun claims EJB Container Managed Persistence solves the impedance problem. How is this different?
Is 2 ohm or 4 ohm impedance better for a sub?
Can bioelectrical impedance analysis identify malnutrition in preoperative nutrition assessment?
Why will I have one child attending Clear Brook High School and one child attending Clear Springs High School? Why is there no exception for students with siblings currently attending other high schools to enroll at the same school as their sibling?
Input Field With Custom Input Method?