Replacement for this FET?

Okay... so long story short, i have this little transistor that i need the non-surface mounted version of. The part # is PHD3055E. I can only find the datasheet, And can't find it anywhere for sale. So i thought i'd come here and ask, Any ideas on what could replace this? Here's the datasheet in the google docs viewer.;;=en≷=us&pid;=bl&srcid;=ADGEESg3724yaKjv666t2rqjyyXVjvQp5HpfKIXr3723cJt4Y_bqPXypg_oySVo3Q9eOgiMBHIG4zDYsHVk73N0whYfHI3PTtv8kTeA_FzIxSWhNnkzgniEWSIQLls8aeQVgmyBDhZyI&sig;=AHIEtbRm4XdPQEc-wzTiPkqsGwSO1qblnA

Question by ReCreate 8 years ago

For FET of n-chanel Idss current is maximum but i found it to be as minimum? Answered

For FET in n-chanel i found that as i incresses the Vds of transistor  the depletion layer of the both pn junction increases .due to this less no. of electron crosses the channel.when both the depletion layer touches each other then Idd current will flow which is maximum possible current through the drain which is approximately equal to zero mA.but as tge depletion layer touches each other there pass very few electron .so as the less number of electron pass current must be minimum instead of maximum  

Question by vivekbittu77 8 years ago  |  last reply 8 years ago

1MΩ Voltage controlled resistor?

Is there any good way to hook up a fairly wide range voltage controlled resistor circuit? So far, I've considered FETs and OTAs. I only have chopper FETs on hand and the datasheet does not list the Pinchoff Voltage. The OTA resistor setup still seems confusing to me.  These will be used in a Voltage Controlled Oscillator circuit.  Any ideas? Am I on the right track?

Question by 8bit 8 years ago  |  last reply 8 years ago

Why a complex circuit for Simple amplification? Answered

Why does a amplifier need so many different parts (like capacitors and chips), I understand that some amplifiers need to amplify a certain frequency but why couldn't other amplifiers just use one transistor or one FET with a heat sink?

Question by squirt8500 9 years ago  |  last reply 1 year ago

Low power mosfet replacement problem

Can anyone help me identify a substitute for a mosfet? It is used, as far as I can tell, as a low power DC switch. It is a 6 legged SMD beastie, part number FDC654 - possibly with a P on the end and is completely short circuit. I'm assuming I've got the right device. There is some information about it here: I can't find anywhere to buy this component as an amateur, and don't know enough to work out a suitable replacement. Can anyone help?

Question by throbscottle 8 years ago  |  last reply 8 years ago

MOSFET(metal oxide field effect transistor) please can you tell me why all of mine are short-circuit?They are new!

I have bought 2 mosfets (irf z44v and irf 540) and the drain is live even when the gate is not connected to anything or 0v?

Question by 12V 9 years ago  |  last reply 9 years ago

What's the difference between N-channel and P-channel?

I'm new to the world of electronics (though learning something new every day) and I've seen a lot of references to either N-channel transistors or field effect transistors, but I have been wondering what the difference is?  If someone could explain to me how the two are different in electrical characteristics, as well as in their applications, I would appreciate it immensely.

Question by KentaGrace 8 years ago  |  last reply 2 years ago

Need help with JFET preamp and chossing transistor ? Answered

Hello .I'm having some some problems with my current project .Can you guys help me please ! This is the schematic of MXR headphone amp for guitar .I don't have 2n4401 and 2n4403 , so i replace them with 2n3904 and 2n3906.The result is output is too low .2n4401 and 2n4403 (collector current = 600mA) ,2n3904 and 2n3906 (collector current = 200mA).If i replace the transistor with higher Ic i will have louder output ??? Thanks for advance! Sorry for my bad English!

Question by login721 6 years ago  |  last reply 6 years ago

Where can I find P channel power MOS-FETs?

I have been able to scavenge plenty of N-channel silicon power MOS-FETs from discarded power supplies, monitors, TVs, and amplifiers. It is rare to find P-channel in these things. What sort of junk electronics should I be looking for? ~Bob~

Question by ShutterBugger 10 years ago  |  last reply 10 years ago

MPF102 replacment for a Ghost Detector? Answered

I was gonna build a simple one LED device that can detect a static charge (which in Theory ghosts give off a static charge making the LED to go dim) using this MPF102 FET Transistor, but Radioshack doesn't sell these anymore, is there another different FET that works as the MPF102 FET one? I was gonna try this one;=3 - but not sure if this would be a great replacement for detecting a static charge like in video saying I need this MPF102 one. Here's the Video Explaining this -

Question by SuperScourge 4 years ago  |  last reply 4 years ago

MOSFET question

Greetings everyone, I've been trying to learn how to use MOSFETs lately, and I've reached a confusing speed bump.  My main objective for a first project will be to simply use it as a switch, but I'd like to really learn them and not just mimic others' work.  The MOSFETs I have are mostly IRF740, IRF540, and IRF240.   Are 'Enhancement' and 'Depletion' modes of MOSFET operation, or see they separate components?  In other words, can I use any MOSFET in either enhancement or depletion mode? My brain and I thank you!

Topic by Electron_flow 3 years ago  |  last reply 3 years ago

star wars

Are there any othere star wars helmate instructables? good one like the bobba fet helmate

Question by jerico420 9 years ago  |  last reply 9 years ago

How to make a solid state FET Amplifier, 600 watts output, continuous 1.5-22MHz cov. swr protected, thanks Mike,,KJ4ITH?

Would like to have a nice solid state amp, but the cost is out of my range, anyone know how to put one togather, and at a savings...they run about $1500. thanks, Mike,,,KJ4ITH

Question by mikie1946 8 years ago  |  last reply 8 years ago


The FET gate gets charged and lights the LED until R2C falls below 66%

Question by iceng 1 year ago  |  last reply 1 year ago

Power Inverter No Load (Idle or Standby) Current?

Hi Instructables members', Case 1: Recently build power inverter have a no load current vary 0.4 to some 4.0 amps (up and down or not stable) which causing the AC ouput also vary 230VAC ~ 235VAC. Case 2: My existing purchased inverter when switch on the no load current stay high. Some where 3 to 4 amps with the FET on power stage remove. Do anyone experience this? Where shall I begin troubleshoot. P/S: For Case 2 - earlier when switch on blown fuse. After change pre-boost FET, it no load current stay high. Thank you for those valuable reply. Finally I found the problem. Case 1: Remove the fan and ad 100uF to ground at pre boost stage. Case 2: Replace an open transistor at pre boost board that driving the push pull fet.

Question by GearUp 1 year ago  |  last reply 1 year ago

Over voltage on Speed controller? Answered

Hi, Today I found out that my electric scooter has a 36 volt motor and it has a 24 volt speed controller. I'm sure it is 24 volts can I over-volt it to 36 volt with out causing harm it has been OK for a while now but I'm thinking of the poor capacitors there only rated at 25v and that why I dont think it will matter as normally there rated a lot higher than that for a safety margin also sealed lead acid battery's have a nominal voltage of 24v and there charged voltage anything up to 30 volts, I,m just hoping that the MOS-FET's that drive the PWM (pulse width modulation circuit) are rated over 36 volts

Question by Daniel Deacon 7 years ago  |  last reply 7 years ago

Using the IRS2110 for 36v H-bridge? Answered

So i have some 850W 36v DC motors that i need to design an H-bridge for, and ive decided to use the IRS2110 to driveing them, since i need to drive the highside fets. I however have no idea of how to use that chip. Any help? :P

Question by dumle29 7 years ago  |  last reply 7 years ago

SMPS H-Bridge trouble

Hi,  I've built a 1kW SMPS designed to take a 350V unsmoothed DC input and convert it to 3kV @ 300mA. The circuit is basically Uzzors2k's design seen here minus the overcurrent protection and smoothing capacitor (for now), however I accidentally wired the GDT outputs backwards so the gate resistors (33ohm 2W) are on the source. I have used alternate MOSFETs the latest attempt with FDPF16N50T's. I've had various problems with the circuit, primarily the MOSFET's exploding seemingly from overvoltage (evidence of flashover in some cases despite no evidence of secondary leakage (i dismantled the transformer to check)). During my last test I had a flashover between the drain and source pins of one of the FET's, in addition all of the gate resistors were smoking hot after, seems the gates had all been shorted (first time this happened, other occurrences were from case to ground). This happened despite the variac only being turned up to 40% which should be well well below the pin spacings maximum voltage tolerance. I have checked the drive signals, they are quite nice square waves at about +-15V with some oscillation on their rise. I have built SMPS's before, one is currently working with similar MOSFETs using a half bridge at 300W. Does anyone have any suggestions as to why these troubles are occurring or have any suggestions to fix it or have any alternative circuits that may be less troublesome (is a h-bridge easier to manage?)? Thanks, Stephen I​ just gave it another test with a H-bridge instead and the source of one of the FET's blew so it appears that there is just FET failure and maybe not arcing between drain and source.

Question by The MadScientist 2 years ago  |  last reply 2 years ago

SMPS failure, the Gates of the MOSFETs exploded?????? Answered

I've just build an SMPS using a TL494 chip using the power circuit from this circuit from uzzors2k, it's just a standard half bridge in my case using IRFP460's. The MOSFETs are driven through a small transformer that itself is driven with a H-bridge.  Yesterday I was trying it's first mains power test slowly ramping up the voltage with a variac when at about 180VAC i could hear some fizzling from the circuit and at 200V the GATE's of the MOSFET's exploded violently, at close inspection there was no shorts or flashovers and the gates were the only thing that was damaged at all. One thing i noticed later was the output waveform of the power transformer, unlike the signal waveform it didnt exhibit the same 96% duty cycle but a 100% with a lot of ringing on the rising peaks of the square wave, i know this can probably be fixed by reducing the duty cycle but i cant see how it could've blew up the gates. I've included some pictures so you can see what i mean by explode, as you can see on the left Fet the gate pin has completely blown off and the copper has melted slightly and the right image the same happened but i cracked the Fet open with a hammer to see if there were any clues inside. I really dont have a clue why this happened and would appreciate some help, thanks in advance.

Question by The MadScientist 3 years ago  |  last reply 3 years ago

12 volt Charge controller (solar)?

Hi i am wondering how to go about building a solar charge regulator i need some help and passably schematics i have 2 broken charge controllers  the parts i have salvaged  11A20YR, LM324. IC x2 11YRD g4, CD40106BM. X2 IC IRF3205, MT 1D4H. X6 MOS-FET ALJ, D882, P63. X2 TRANSISTOR X16, GF1200, YELLOW THING X2 C1115, JC817,KENTC, X2 few other parts that are on the board

Question by Daniel Deacon 7 years ago  |  last reply 7 years ago

Can someone help me find the data sheet for this transistor? Answered

I recently purchased a few grab bags from Jameco and I can't seem to identify one of the transistors that came with one of the grab bags. So far I have figured out it's a Motorola brand possibly a FET. I attached a picture of it with the part number which reads M9943 m828. The m before the 828 is the Motorola logo letter M.  I've tried searching Google, JameCo, and the Motorola website for this part number; but I have not had any success at finding a datasheet for it.

Question by atrumblood 7 years ago  |  last reply 7 years ago

Limit DC current from LiPo battery?

Dear Colleagues,  could you please advise if there is a way to limit DC current from LiPo battery?  I need to push the high current (80A) through very low resistance circuit, but do not want to fry LiPo. So need to limit the current at 80A I am not an electronic professional, and all solutions coming to my mind are based on increasing resistance of circuit (by adding resistance manually, or constructing something like FET-regulated limiter). The problem here is that I will generate lots of heat, and need too much space for its dissipation.

Question by SergeyD15 2 years ago  |  last reply 2 years ago

Voltage regulator Design Problem?

 Ah, voltage regulators. Easy Right! Not this one. I am making a voltage regulator like for an automobile regulator for a DC generator. (I'm replacing the old DC generator regulator on Pre 60's cars) A battery is charged from a winding on a Generator  (20V @ 60 Amps) A voltage sensor on the battery voltage turns on and off a switch driving the Field winding. The Field winding basically "turns on and off" the generator output. The battery is connected directly to the generator. (Why  and Why not is coming up) But when the Genrator's output is lower than the Battery voltage, current will flow back from the battery to the generator winding and discharge the Battery. So I need some isolation between the generator output and the battery. Alternators are easy since it has a bridge onthe output keeping the current from flowing backwards. Old regulators used a relay which burned out sooner or later. So easy, use a diode right? Just put a diode inseries with the generator to the batery. By the way, the "open circuit" voltage on a generator is about 200VDC No! The best diode I can find has a .7V drop at 60 Amps which is 42 Watts of heat to dissipate. Ahhh, so use a FET, They can get down into the milliOhms right? Except for the reverse polarity (and ESD) protecton diode always across the FETs defeat the purpose of a reverse polarity switch. So who out there is smarter than me? What goes inthe box marked ?? Any solutions accepted. Ungefahrt (now neither young or fast)

Question by ungefahrt 6 years ago  |  last reply 6 years ago

Need help to build a sound amplifier

I would like to build a sound amplifier for my computer's headphones (main reason for experimenting and to use it too). I would like a high power amplifier with maximum of 12V supply(since i'm going to connect it with my computer's power supply) I would like your help as i'm "new" to electronics to answer my question. -Should i use an IC or i build it with transistors?      - If with an IC can you suggest a suitable IC.      - If with a transistor, what type of transistor BJT, or FET? Suggest a suitable transistor. If possible please post a diagram of the whole circuit with the IC or transistor you suggested. THANKS before hand.

Question by h3llkill3r 9 years ago  |  last reply 9 years ago

Can I replace the transistors in this LM723 regulator circuit with MOSFETs? Answered

I am trying to build a power supply capable of outputting up to 15V at 10A. The heatsinks I have are not suitable to use with the 2n3005s TO-204 case. Also I can get IRFP250 MOSFETs a lot cheaper. The transistors I want to replace are Q2-Q4, Q5 I will not include because I only want 3 FETs because I only want a 10A supply not a 20A.  Here's the link:;=2&TPN;=1;=2&TPN;=1

Question by The MadScientist 6 years ago  |  last reply 6 years ago

Cree XB-D driver circuit

Hi Everyone,I would use following design with some modifications to be able to drive 3x3 Cree XB-D LEDs Green/Blue: Step 8 #4I would use 12V ATX computer PSU as voltage source.PWM source: Arduino nanoAttached picture show how I modified the design: 3x3 LED setupMy main concern, is it correct my calculation of LED currents: based on my understanding, 220mohm current sense resistor setup 2,272A current through FET. Based on Kirchhoff's current law, it will be 757mA for 1 LED.Is that correct?Any advise and suggestion would highly welcome.Thanks,Best Regards,Gyorgy

Topic by bernathg 10 months ago  |  last reply 10 months ago

cnc router stepperworld controller- need how to wire help ?

New to this site, I really need someone  to help me figure out how to wire a  3 axis stepperworld FET-3 controller to 3- rapidsyn division american precision motors model 23D-6137H 11.2 VDC .44AMP 6 wire=  BL, W,  R, G,  W/R STRIPE,  W/G STRIPE do not have powersupply yet , please advise I am looking at a 24 volt on ebay. Below are pictures of motor and controller   can upload more pictures . [IMG][/IMG] [IMG][/IMG] thank you , marty

Topic by mrmartyman7 8 years ago

Audio Priority Switching Circuit. Can not find a schematic that will fit my need

I have searched but came up empty. Here is the need. 2 audio lines coming in. 1 is on all the time. when audio is sensed on line 2, it will reduce (or turn off) line 1 allowing line 2 to take priority. Then when line 2 stops, (mobile radio traffic) it switches back to line 1. The challenges: Small as possible (and yet I can still solder together) runs on 5-9V DC Adjustable gain on inputs Sensitivity adjustment on "switching" function Of the hundreds of circuits I have looked at, It seems to be a fairly simple task with a FET ......  I can build it, but the design portion is a to much math for  A 3 audio switching circut would be AWESOME!!! Anyone seen anything out there that will help me in my search??? Thanks, Steve  

Question by Sadputter 7 years ago  |  last reply 1 year ago

Controlling a motor with PWM

I'm building an ROV for the MATE ROV competition with a high school team this year.  For this year's competition, we've decided to control our bot via an Arduino Mega, and we're using PWM to potentiate the thrusters.  As the person designated to electrical, I fortuitously have no idea how to set up an intermediate step from the Arduino to our thrusters.  I've looked into H-Bridges with both Relays and Transistors, and defaulted to the transistor. How would I choose what transistor to use though? I've tried several (all BJTs) and they're giving me nothing but problems.  Should I switch to a FET? Should I use a P type and an N type, or only one?  What specs should I purchase them with?  Do I ask too many questions? Help!  (I'm trying to control a 12V 6A motor with a 5V Pwm signal. Thanks!)

Question by unununium 8 years ago  |  last reply 8 years ago

Mains Ground Safety for Power Supply? Answered

I'm trying to build my first switched mode power supply. I'll be using it to drive two 24v 50W heating elements. I don't want to use a transformer. The design I have so far seems to work well in simulations, but I need some advice regarding mains ground. The control electronics will be operated on power from a small transformer. This provides isolation from mains. I've done this a million times.  However, the mains power connects directly to the loop that produces the 24V signal. This is the loop after the FET, containing a diode, inductor, and capacitor. The wire coming from this loop and going to the comparator is where I'm having trouble. This is a voltage sensing wire and carries very little current, and is used by the comparator to produce negative feedback. This feedback loop is what allows me to get 24V from 120V. The comparator is powered by the 12V isolated supply. In order for it to sense the voltage properly, the comparator's ground must be at the same voltage as the power supply's ground. But the power supply's ground is tied directly to mains ground. Is that safe? Am I allowed to do that? In mains wiring in the US, the left notch is neutral, the bottom hole is ground, and the right notch is hot. Neutral is basically ground, except ground is connected to the actual ground and neutral is this mysterious thing I probably don't completely understand. Is it safe to use it as ground? What if the person using this circuit flips the plug over and suddenly the circuit's "ground" is fluctuating wildly between +/- 120V? The circuit may function just fine, but someone using a switch or knob connecting to ground could get a nasty shock. How do I make sure the ground of my circuit is always connected to actual ground? Do I need to preserve the isolation of the control circuitry? I know how to use Gate Drive Transformers for the FETs, but the sense wire for the comparator still needs to have both halves of the circuit with their grounds at the same voltage. Any advice is greatly appreciated.

Question by laserjocky 5 years ago  |  last reply 4 years ago

gate driver for power mosfet

I am strobing columns of LEDs at high currents very quickly (100mA for each LED, for 100us) with p-channel mosfets and LED drivers. The p-channel fets that can handle that sort of current (100mA * 24 LEDs) have gate capacitances of 1000pF and up. My microcontroller can't push too much current to the gate too quickly, which would result in the mosfet losing power to slow switch (and ghosting in the LEDs). I KNOW that some sort of gate driver buffer ic exists, i just can't seem to find one. Everything I am finding is for high-voltage or high-current applications and motor-driving. I just need something that will drive my gates at 200-400mA, and since i need 9 of them, i'd like them to be cheap. I dont need any of these motor-driver ICs or 3A gate driver chips... Can anyone help me out?

Topic by samurai1200 9 years ago

I'm back! And I've got a challenge for you!

Hello Instructablonians! I'm back (at least for the next few weeks) since it's winter break!  MIT is fantastic, and I've learned so many incredible skills that I think I'll be able to participate in my new challenge. The Challenge:    * Your job is to produce about one (quality) instructable per day for the next 11 days.  Instructables are allowed to be backlogged (ie. do the project in one day, take the pictures, but wait to write the instructable), so long as they are posted by January 17th.  I'll also give you 1 day of lee-way, so you only have to make 10 ibles total to qualify.  Make sure that you tag your instructables with the keyword 'muffinchallenge09'. The Reward:    * Ever want pseudo random components that can fit in an envelope?  If you're in the US, I'll send you a letter with a card and some components you can pick from a list that I'll post when the contest is over.  (Mostly stuff like LEDs, old logic components, maybe some FETs or BJTs, crystals, etc.)    * A Muffin Challenge Digital Patch of Approval!    * The satisfaction of being incredibly productive this season. So get to it!  Happy Snowydays for everyone in the Northern Hemisphere! -muffin p.s. How to catch a bird at the top of a mountain?  :-P

Topic by T3h_Muffinator 9 years ago  |  last reply 9 years ago

How to select transistor?

Hi guys! How do you know which version of transistor to select when it comes to doing some projects? I mean, lets say i have all the parameters of my project, the output current and voltage, so how do you know which specific model of transistor to select from the data you have? Is there some kind of list from which we can select the required model from our data? For example, i have an LED array which draws about 90mA of current in total and has a total operating voltage of 15V, and from past instructables that i read on this site, i know that BC547 has a current rating of 100mA and can tolerate the voltages, so i can use it. My question is, that suppose i didn't read these instructables, then how will i know which transistor or FET i have to select that has a current rating of about 100mA and can tolerate the voltages(i.e how will i know that i can select the BC547 or alternative)? Also, when selecting a diode for example, i know from reading few instructables that 1n4007 has a rating of about 1A and can tolerate good amount of voltages. Suppose i don't know about the diode, then how will i know that based on my requirements, i can select the 1n4007 diode? This is an example in general, and it applies to all cases of load currents and voltages, and other semiconductor devices.

Topic by charmquark 6 years ago  |  last reply 6 years ago

EG7500 Inverter Drive Board Testing and Query?

Specification EG7500 Inverter Drive Board. PWM freq 40kHz. Overvoltage shutdown 15V +-0.5V. Low voltage buzzer beep 10.5 +-0.5. Undervoltage shutdown 9.5 +-0.5. Overcurrent shutdown 48mV. 1A Output current drive. Carry out a test by varying DC between 9V to 15V. Resulted: 1. At 10V to 10.5V buzzer beep. "OK" 2. At 9V to 9.5V or below 9V the unit shutdown. "OK" 3. At 13V to 13.5V ran into off and trying to restart the unit (Board marked A). "NG" 4. At 14.5V to 15V ran into off and trying to restart the unit (Board marked B). "OK" Refer to above test how to improve "Board Marked A" overvoltage shutdown?  Which part of the schematic to begin troubleshoot. What component I needs to change or improve?  Once power up. This unit draw ~0.5A on standby. How do I minimize the standby current? There are no temperature control since P3 "S8550" was not on board. Can I just put "S8550" on board and use PTC for temperature control? As proposed by schematic online, pin 4 fan control feet to ad 100uF to ground. How do I change this part to enable fan control once the temperature rise? How many FET this unit can drive with 1A at 40kHz? How to test the overcurrent shutdown? Thank you

Question by GearUp 1 year ago  |  last reply 1 year ago

expanded graphite heat-sink? Answered

Okay , I've searched and searched and cannot find what I'm looking for. Maybe the other diy'ers can help me. 1.What I'm looking for is a heat-sink made of expanded graphite or (carbon, graphite (∥) as it might be known as well) that is actually in the shape of a traditional aluminum heat-sink with the fins and NOT in the shape of thin film as it is very commonly available. I don't even know if it exists or is manufactured by any company. I've tried contacting some companies about it but they have yet to get back to me. The reason I want this is for the tremendous increase in heat conductivity as in this chart shown on this webpage . The application I am trying to use it for needs a raised, elongated surface area to displace heat semi-uniformly, hence why I need fins like a traditional heat-sink instead of the commonly available film expanded graphite online. 2. If it does exist or is able to be manufactured, would it be a ridiculously priced part or would it be a reasonable priced part? (Just doing small scale tests for now so it would be the size of a FET finned sink). 3. From what I've read it seems possible by maybe layering the films into a stacked lattice, keeping heat transfer perpendicular to the lattice, but what are your thoughts all? (I question bonding the layers myself but I don't know if you could hard press the layers together without a bonding agent since any bonding agent being used I believe would reduce the thermal conductivity quite a bit, but I'm not incredibly familiar with expanded graphite). Any and all help would be appreciated from this wonderful community Best regards, Velesh

Question by velesh 6 years ago  |  last reply 6 years ago

Current limiting high voltage - ccfl inverter help ? Answered

Okay as my first question i'll say hi first , and Darren from Ireland here , fair "know how" of electronics and how things roughly work. I have a 32inch TV who's inverter board is toast (okay its going on and off straight away) , I know its getting power from the psu board as there is little or no voltage drop when I flip the TV on and the lights fire up. I have asked 3 people at work (Electro techs at work) and they all say the same thing , replace the board , its too much work (I think there just lazy) and also they all say they would need the data sheet on all components or the circuit diagram. So well me with my stupid head wants to try and have a stab and getting a free TV. So I have ordered a CCFL inverter power source for a neon case light , which I intend to use just to see if any one bulb is gone as im not sure if that is what could be kickin the inverter off. And the other thing i have ordered is a "Universal inverter for 10-30v 4 bulb 17-24inch" from ebay. So the question is , if one bulb is gone and well i doubt i can order a bulb like this and replace as that would be end of tv if i open than panel . is there a way to simulate that bulb working in any way to stop the inverter going off because of one bulb. And the other question is , if I want to use this universal inverter , what is causing it too be a 17-24 inch only ? From what I understand is if I am wrong correct me please , that the larger bulb would burn the driver chips/fet's drawing too much current. So would there be a easy / safe way to just limit the out put so they will run but a little dim (as the tv is intended to be used in a dark room any way) Any ideas welcome , and for what ever comes up , Thanks !

Question by dwoods-1 6 years ago  |  last reply 6 years ago

BJT vs MOSFET? Answered

-- background: In my perpetual pursuit for designing the best, cheapest, & best performing flyback (line transformer) driver, I've decided to try out some big BJTs, which appear to have higher voltage & current ratings @ considerably lower cost. In the past, I have tried MJE3055's, which work OK, and allow the generation of thin blue arcs from a 12V supply for a few minutes until the transistor dies due to high voltage kickback or overheating. The FDP33N25 gives good results but is somewhat unreliable at 24V. So I decided to give these alluring "PHE13009" 400V 12A rated NPN BJT's a try. However driving the transistor adequately seems to be the problem. (I didn't realize these transistors would require like 5A base current w/ only HFe of 2!) It seems like almost all the "good" driver schematics utilize large $$$ FETs or even IGBTs, but almost every CRT, plasma globe, and ballast (SMPS) I took apart seem to prefer high power BJTs probably due to this exact cost difference. I was only able to get simalar performance to my 33N25 MOSFET when I stuck an additional TIP120 in as an additional darlington stage, which worked very nicely (white hot arcs) for about 1 second, then it popped! :( Since the collectors are tied together they are all exposed to >200V transients, I am sure that's what killed it. I substituted that transistor for another PHE13009 to see what would happen and with a third driving stage (2N2222) I could get somewhat acceptable results but I know I can do better. >:) - My actual questions:  * The GDP of this transistor is 40MHz, seems fast to me. (certainly faster than the 2MHz GDP of the 2N3055 which works well in my slayer exciter.) and MOSFETs have significant gate charge. ECE2630 glossed over transistors mentioning BJTs are faster, (small signal ones, anyway :P ) and some internet sources agree, but I am finding lots of sources saying the opposite! What's the deal? Which one "faster?"  * How to traditional BJTs compare to IBGTs? Which are faster/better? The datasheet for this transistor explicitly mentions its use for "high frequency ballast and switch mode applications" which implies that it is well suited for my needs. It also includes a several inductor test circuits, but other than that the datasheet is pretty bare-bones.  I'm actually a little disappointed the HFe is so low (around 2-3) @ >10A. I may require more windings on my primary and a 48v supply. (not ideal) * I know I will dissipate a little more heat due to the base current, and something I didn't consider was heat dissipated in the resistor biasing/controlling the base. (like 12V at several amps just to drive the damn thing!!) so it is worth the cost benefit of $0.5? Is there a configuration I could use that makes driving the transistor easier?

Question by -max- 2 years ago  |  last reply 2 years ago