lots of talk about mosfet regulators. what is it? why is it better? mosfet is just a type of transistor. nothing else. it serves the same purpose as any transistor. it's an electric switch that amplifies voltage. a tiny electrical signal turns the thing on and allows lots of current to pass through the thing. it's an electric solenoid.
so does that mean the bjt transistor is antique. no way. it has properties mosfets don't have. bjt's can be wired emitter follower. emitter follower regulator is the led driver.
so why are all the modern regulators mosfet. all the reasons are practical. cost, they are much cheaper to make than bjt power transistors. they pass more current. the irfp250 25 amp mosfet costs like 5 for 5 bucks. they are easier to heat sink. the t03 case on the power bjt needs 5 precision holes to mount and an insulator with special bushings. the mosfet needs only 1 hole to mount and is electrically isolated. no insulator needed, still needs a bushing though but only one. the bjt needs 4 nylon bushings.
like all electronics the newer mosfet transistor is cheaper, easier, stronger but not better.
A field effect transistor has a much lower voltage drop while carrying current, so it generates much less heat than a bipolar transistor.
MOSFET = Metal Oxide Semiconductor Field Effect Transistor. The ones I use in the regulators I manufacture are National's version called HexFETS, that have a hexagonal cell structure.
I also use Schottky diodes in the rectifier for the same reason, lower voltage drop and less heat.
Quote from: Jim on April 20, 2019, 12:49:18 AM
A field effect transistor has a much lower voltage drop while carrying current, so it generates much less heat than a bipolar transistor.
MOSFET = Metal Oxide Semiconductor Field Effect Transistor. The ones I use in the regulators I manufacture are National's version called HexFETS, that have a hexagonal cell structure.
I also use Schottky diodes in the rectifier for the same reason, lower voltage drop and less heat.
cool, looks like I found a friend on the forum. physics. these devices are real and each one has different properties. mosfets use no current to do it's job. bjt's need current to run. to put it in plain language it's an electric solenoid. one will trigger with static electricity the other needs a wire run to it.
this property is real but useless on a bike. its for having long battery life on cell phones and laptops.
motorcycle physics. class is in session. ha ha. a subject you can only find on 2sw. I have the freedom on this site to talk shit. the only time I'm worried about parts using too much juice is at idle. ask anyone who has tried to run a honda twin without a battery. its because the voltage at idle is below the charging voltage that mark took a pic and posted 14.3v, many years ago. whats my point? either regulator bjt or mosfet are off and both use no current when it counts, below the trigger voltage. regulators are wired parallel to the load at idle, either regulator uses no current and are turned off.
I don't make my own rectifiers because the sql40a is such a strong piece of kit. 40a and the main stock fuse is 15. I don't even bother to fuse my batteryless bikes. I don't think the stator puts out enough juice to smoke that sucker.
please give us a part number for the hexfets you use. I found the irfp250 by searching the net. I'm sure you know your stuff.
IRFP44N
Quote from: Jim on April 20, 2019, 09:26:03 AM
IRFP44N
I knew you know your shit. n channel power mosfet! thanks. no one knows everything, these boards are how we help each other. looked at the data sheet. irfp44n is 83 watts. the irfp250 is 180 watts.
you might want to check out this part.
if you don't know what we are saying don't worry. you do not need any engineering skills to be a mechanic. also no wiring harness needs to be molested to wire modern12v. I've got it down to just a rewire at the rectifier. read my posts and I'll explain more. now that I've learned bbcode take that as a threat. much much more.
if anyone wants deep theory just ask and I'll draw some diagrams. its not necessary. there is a guy on this site that runs his lights on a power dynamo with 4$ scoot regulator. he has the right idea.
Quote from: Jim on April 20, 2019, 12:49:18 AM
A field effect transistor has a much lower voltage drop while carrying current, so it generates much less heat than a bipolar transistor.
MOSFET = Metal Oxide Semiconductor Field Effect Transistor. The ones I use in the regulators I manufacture are National's version called HexFETS, that have a hexagonal cell structure.
I also use Schottky diodes in the rectifier for the same reason, lower voltage drop and less heat.
Thanks for that info, Jim. MOSFET is an acronym I have seen many times over the years and I just accept it as an acronym that means something important. Now I know it's Metal Oxide Semiconductor Field Effect Transistor. Don't ask me what that means, except I'm vaguely familiar with the transistor concept.
Hawaii-Mike,
sorry, bjt is an acronym also. in about 77 or so the transistor made its way into motorcycle regulators. bjt stands for bi junction transistor. in the early '80's radioshack was a store were ham radio types like me went to buy crystals for radios, solder, wire and such. old time electronics were repairable so there was a market. the popular bjt power transistor they sold was the npn 2n3055. npn is an acronym that got basterdized by us tech people. we say not pointing in. its the symbol we draw.
at about 2005 or so the switch to mosfets in high power devices. besides their low power drain they have properties that make them better in regulators than the bjt's. the specs of the one I'm using today is amazing. 180W@25 amps. the cost is amazing too. the 2n3055 cost $3 in the '80's the irfp250 costs like 5 for $5.50. irfp250, irfp44n, 2n3055 are part numbers for transistors.
all of this info is useless to a mechanic. a mechanic would just buy the correct regulator and wire it in and not worry about the tech. what I mean is if you have a john deer tractor and you need a new rec/reg the type of tech inside is not a factor. who cares if the old part has 2 bjt's inside and the new part has 1 mosfet. from the outside the part is identical and the specs are the same on the inside.
Mike gets a treat. transistor concept for a mechanic. think of the thing as a normally open switch. push the switch all the way and the switch closes. you can press this switch like a dimmer switch. half way is half closed. the springs on the switch are different. the mosfet has a hair trigger.
Typo, it's an IRFZ44N. The dissipation rating is 94 watts. It's good for a continuous 35 amps at 100 degrees C. With a drain to source on resistance of 0.0175 ohms and a 7 amp maximum current in this application, I ask it to dissipate about 0.86 watts in the worst case. The 94 watt spec is meaningless in this case.
Quote from: Jim on April 22, 2019, 12:05:13 AM
Typo, it's an IRFZ44N. The dissipation rating is 94 watts. It's good for a continuous 35 amps at 100 degrees C. With a drain to source on resistance of 0.0175 ohms and a 7 amp maximum current in this application, I ask it to dissipate about 0.86 watts in the worst case. The 94 watt spec is meaningless in this case.
again you know your stuff and taught me something. now lets let other people know. first off we are both right. why? because the specs are crazy compared to old tech. IRF stands for the company international rectifier that make these chips. IRFz44n and IRFp250n are transistor part numbers.
the stock main fuse is 15a. the IRFp250n will blow out at 30a peak. Jim's IRFz44n blows out at a whopping 41a peak and can run 35a continuous. this is the maximum drain current read from the data sheet.
the 94 watt rating is meaningless until you exceed it and blow the part but there is no way this will happen.
IRF is also meaningless. the international rectifier company was bought out in 2014 for $40 dollars a share on the nyse. this chip is made by a different company but the part number sticks so everyone's tech manual is not screwed up.