N Channel MOSfet

713

15:34:37

Basic usage of N Channel MOSfet. When the Gate is connected to Ground then MOSfet stops current flowing. When Gate is connected to Positive then MOSfet lets current flow and the Led lights up.

 IRFZ44N and IRLZ44N are very common MOSfets to use with arduino-like systems because the Gate voltages are suitable with 5V logic degree of arduino power and signal voltages. Especially IRLZ is more suitable because of its a Logic MOSfet and so the threshold voltage of Gate gives more accuracy on contolling current.  Same result can be taken by using PWM with the IRFZ serie. Chosing the way is up to you ; A pot with L Serie or to use PWM with F Serie. To use MOSfet as a dimmer. 

published 8 years ago

ViolationMad

8 years ago

The current Ids will stay roughly the same when the voltage Vgs is konstant, isnt it?

2ctiby

8 years ago

@ViolationMad ... Yes it will here because that Ids current is being limited by the resistor, just as it would be in a simple circuit without a mosfet. If that resistor or the Vgs is altered then the Id current would change.

techdesigner

8 years ago

@ViolationMad with the change of Vgs from 0v to 5V you can change the current that Mosfet lets through, of course via the min and max limits as told in datasheet ( threshold min, max ). But changing Vgs surely controls Ids thats the logic of mosfets, but again of course the resistor controls the Upper limit. But also changing the resistor surely effects the current for sure as 2ctiby said.

ViolationMad

8 years ago

@techdesigner Yeah thanks for the reply, but i was actually thinking more of a linear relation between Vgs and Ids. I dont know why but yesterday i woke up and my mind is just blocking. I cant really figure out the regions of operations anymore... Can you compare the Ohmic region with the activ region of a bjt? And is saturations actually the same either? Cause i know that a bjt saturates when Vbe>Vce and there is current flowing from B to C. I just cant understand the N-MOS formulas anymore.

techdesigner

8 years ago

@ViolationMad. The relations that you are curious about can be found in datasheet as graphics. Try datasheet of a Logic MOSfet ( IRLZ44N )

2ctiby

8 years ago

@techdesigner ... Your schematic here displays nicely ... you might want to think about raising the Vth now to a more realistic value for a general Mosfet... it is only a technical venture here though, because your Nmos Rds of 37.1 mOhm is reasonable at that present value. ... As a practice, you could raise the Vth to 1V and see if you can keep that Rds the same.... then see if you can set the Rds at 0.022 Ohm which is mentioned on the IRLZ44N datasheet.

2ctiby

8 years ago

@ViolationMad ...I would advise that you forget about bjt comparisons when learning about mosfets...it could cause more confusion than it is worth, due to dissimilarities. At your stage (suggested by your mentioned confusion), I would suggest also that you shelve any thoughts about the relationship between Ids and Vgs for now. Instead See here http://everycircuit.com/circuit/4722063570108416

techdesigner

8 years ago

@2ctiby yes you are right. Thats just a demonstration schematic for beginners to see the logic firstly, without numbers and deep calculations.

2ctiby

8 years ago

@techdesigner ... agreed ... for general EC switching demonstrations, all we need to do to simulate a real Nmos adequately, is to quickly alter the settings as follows: W.. fully clockwise, L.. fully anti-clockwise, KP.. fully clockwise, VTO..2v, Lambda..no alteration.

GertBowker

3 years ago

I am now super confused, which is the gate

techdesigner

2 years ago

@GertBowker Mosfet in the circuit as you can see, connected to 3 parts of the circuit, Drain pin is connected to the Led, Source is connected to the Ground directly and Gate is connected to the button to switch on and off the mosfet with 5V directly from the battery, drain leg of the mosfet is in the middle and horizontal leg at the circuit. Hope this help.

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