121 Threads found on edaboard.com: Fet Drive Circuit
in battery charger section there is two Mosfets named AO4435 AND AO4409 if i remove the AO4409 MOSfet THEN the charger adapter pin shows me the 18volts reading and if i replace it then it shows 0 volts , and that AO4409 is got shorted I tested it . My question is what is the substitute Mosfet that i can use here and how to solve further (...)
Service Manuals, Requests, Repair Tips :: 25.08.2013 13:57 :: peter_england :: Replies: 3 :: Views: 424
Use a logic MOSfet switch or a semiconductor relay (photocoupler input).
Analog Circuit Design :: 02.02.2009 08:37 :: erikl :: Replies: 1 :: Views: 744
Because unipolar pm2515-03 is restricted to medium speeds by design, any small power transistor (BJT, darlington or fet) can do, also integrated drivers.
Hobby Circuits and Small Projects Problems :: 07.08.2009 04:24 :: FvM :: Replies: 5 :: Views: 3986
You need to hook up a 'scope and look at some things.
First off, huge ground currents need to be kept to very
tight, short loops. If they can, they will corrupt your
analog and possibly digital sections. Among common
behaviors from this, is a reswitching or chatter on the
fet drive signals, which can suck a lot of current.
Second, if y
Analog Circuit Design :: 13.10.2009 21:41 :: dick_freebird :: Replies: 2 :: Views: 845
1/2CV^2 is the energy delivered to the gate, but in the process of charging it through a resistor you will also dissipate 1/2CV^2 (this is independent of the resistor value). Then when turning the fet off, the 1/2CV^2 stored in the gate capacitance will be dissipated in the driver. So your circuit overall consumes CV^2 per switching cycle.
Power Electronics :: 14.12.2011 12:42 :: mtwieg :: Replies: 5 :: Views: 2338
I am trying to work out a circuit to drive the windings of a stepper motor. I have done plenty of digging around and know the basics that I can use wither a fet or a Darlington pair to do the power switching. The problem that I am having is working out the power supply and matching it to the motor I have.
The motor I have is a (...)
Analog Circuit Design :: 18.10.2012 16:56 :: Sailing_Nut :: Replies: 5 :: Views: 279
Do you want to test the optocoupler or the fet? And is this an in-circuit detection, or do you want to check components on the bench?
Power Electronics :: 17.01.2013 10:15 :: mtwieg :: Replies: 6 :: Views: 464
I've been using BJT for a long time, #B#C#3#3#7#, #B#C#5#4#8# 2#N#2#2#2#2# and others... but I've no experience in using fet's, could you experienced guys tell me some models that are cheap, easy to find and TO/SMD package available and multi purpose fets?
Professional Hardware and Electronics Design :: 12.05.2002 09:22 :: 2000 :: Replies: 6 :: Views: 2501
u can also use a small fet instead of a bipolar transistor. But as mentioned before: NEVER forget the protection diode antiparallel to the coil in order to avoid damage of the transistor/fet and the PLD. Those ULN-devices are great but if u want to drive only one relais a transistor might be easier and requires less space.
One good (...)
Professional Hardware and Electronics Design :: 19.07.2002 18:23 :: :: Replies: 5 :: Views: 1388
Yes it is exactly that. A led (or 2 inverse parallel for AC) on the input side. Use series resistor to supply about 10ma. Output side is photosensitive Transistor/fet/SCR ect, depending on type. Isolation is usually at least 2000v. I you give me more details of what you are trying to achieve, maybe I can assist further.
Professional Hardware and Electronics Design :: 27.07.2002 16:55 :: GrandAlf :: Replies: 11 :: Views: 1998
How accuracy do you need? I don't think 1% is required for LED. At this point of view, a power MOSfet and a adjustable resistor will do the job. adjust the pot till the current reachs 1A.
carefully deal with the heat sink issue. the temp may be very high at 48V input.
Analog Circuit Design :: 08.03.2005 09:19 :: aslak :: Replies: 6 :: Views: 3461
The gate drive of SCR will have a low impeadance. The work off of current to drive them not voltage like a fet. You should probably be hitting about 1-1.5 V peak on the gate drive of with the SCR connected. The attached drawing is one that I have done myself. I did neglect to put in all the gate pulses you would get from (...)
Analog Circuit Design :: 01.08.2006 12:24 :: dfullmer :: Replies: 4 :: Views: 957
I'm using a DTMF Decoder kit from Ramsey Electronics
to sense touch tones from an audio channel. I used it to drive relays to trigger pneumatic solenoid valves. Apparently the EMF from the coil turning off was blowing the big chip in the kit.
I have a new circ
Analog Circuit Design :: 08.10.2006 12:56 :: stefano.delfiore :: Replies: 2 :: Views: 1311
It looks like you are trying to build an H-Bridge.See this
You need to pull an N-fet gate above the source by at least the data sheet threshold voltage (Vths) usually with a safety margin as well, and you also have to be sure that at the Vgs you are supplying that the Mosf
Analog Circuit Design :: 09.12.2006 11:22 :: max0412 :: Replies: 1 :: Views: 2281
You need the 555 12v output to drive small N transistor like 2n2222 or N fet 2n7000
The N transistor / N fet connected as inverter driver to power P fet so the 555 12v output will switch on the power P fet on
Analog Circuit Design :: 13.02.2007 01:56 :: Jepeto :: Replies: 7 :: Views: 1522
i think your circuit will meet some problem, if your output voltage will not feedback to adjust the drive signal of the power mosfet
Analog Circuit Design :: 04.05.2007 06:37 :: rfzheng :: Replies: 4 :: Views: 1060
Your mosfet source will allways remain at potential = 28V-Gate threshold of fet - drop across 1E depending upon load current.
In turn your load will never see 28V. - if your application / load accepts that there is no problem else there will not be sufficient voltage to drive the load
Analog Circuit Design :: 10.08.2008 04:33 :: rvionics :: Replies: 7 :: Views: 747
I'm having problems with gate drive transformers. My circuit is the test signal (buck_fire_2) i used 250kHz PWM at 50% duty cycle. The output (gate side) is terible; just a sine wave with about 40V amplitude (which probably destroyed my fet). If I lower the frequency the output is
Power Electronics :: 04.06.2009 10:32 :: Mercury :: Replies: 7 :: Views: 3293
What kind of gate drive circuit do you use ? for PWM inverters you must use a dedicated IC like IR2110, 2113 which can charge/discharge MOS-fet gate very fast. if you used a simple circuit like in modified sine inverter, with just one transistor and resistor for chare/discharge, this is the result.
there are other options (...)
Power Electronics :: 26.06.2009 02:41 :: cristivasilache :: Replies: 6 :: Views: 7700
I have a relay that is driven from a PIC 18F452.
It is driven with a FDV301N N-fet.
I've put a 10k in series with the uC pin to limit current to the fet.
NOW I want to put a pull-down on the pin for when the micro-controller is in
reset and the pin is set as input. so I don't want the input to float, So I want to
Electronic Elementary Questions :: 28.09.2009 11:44 :: treitmey :: Replies: 5 :: Views: 880
You are expecting to much from this poor MOSfet ..
It is not designed to switch at 2MHz (20%) pulses of the duration of 0.1us ..
Also, to switch the MOSfet’s gate you need a proper driver (for example complementary emitter follower) and a microcontroller pin is definitely not the one to do so ..
Take a look at:
Analog Circuit Design :: 01.02.2010 02:17 :: IanP :: Replies: 5 :: Views: 2840
The switching speed of the fet is slow and so there is an extended period where there is voltage across it while current flows through it. This is probably caused by the limited drive current sent to the capacitive gate-source part of the fet.
I would suggest that you use and IC specifically designed to drive (...)
Power Electronics :: 16.06.2010 23:17 :: flatulent :: Replies: 4 :: Views: 1329
Hi, I'm looking for building a custom protection circuit for rechargeable lithium ion polymer batteries.
The three protection offered by the standard PCM are :
- overcharge voltage
- over discharge current
- cut-off voltage
Assuming, the charge voltage is regulated and controlled by the charger IC, the over discharge current is limited by
Hobby Circuits and Small Projects Problems :: 03.12.2010 02:37 :: Argail :: Replies: 0 :: Views: 1038
I have prepared this on seimens IC TCA785
and power module 26 amp 1200 volts one double diode and double SCR
and this works as half bridge.
circuit is similer to TCA785 PDF example but with some changes
I have used fet IRF540 to drive the SCR.
pulse transformers I have build myself. with 2:1 ratio.
when i gives 0 to 10 Volts. it (...)
Professional Hardware and Electronics Design :: 19.01.2011 06:05 :: engineerpervez1 :: Replies: 2 :: Views: 1648
While I was reading the spec sheet, I was having trouble simulating a demo circuit for the LTC4440 (trying to drive a 70 volt high side MOSfet switch). I provided 12 volts input, and drove the logic at 5 volts. I've included the schematic. What am I doing incorrectly?
Analog Circuit Design :: 04.01.2011 15:27 :: MQuadros :: Replies: 2 :: Views: 638
i agree with logic level mosfet solution. cheap stuff and fairly reliable and 74C14 will handle most problems associated with connection between power and digital grounds. i used this for a similar circuit you are describing except my frequency was not static as i used the circuit as an "ON/OFF" switch... but otherwise worked great, (...)
Power Electronics :: 30.01.2011 11:11 :: Mr.Cool :: Replies: 21 :: Views: 3278
I'm working on a video project and I need to reproduce a composite output that matches an existing device (the TMS-9918A if you want to know.) Let me try to be as brief as possible. I am a little confused by the original device's output, which according to the data sheet is:
Analog Circuit Design :: 24.05.2011 01:14 :: TQFP :: Replies: 4 :: Views: 612
Its output is (almost) identical with the input
Yes looks like something is significantly wrong!
- you put in a PMOS instead of a NMOS fet. It' simply acting as a short between input and output
- the circuit won't work with a NMOS fet either, because the gate driver voltage needs to be connected between source and gate (...)
Electronic Elementary Questions :: 19.06.2011 05:17 :: FvM :: Replies: 6 :: Views: 1271
There are no battery condition lights either
Ist see if ground connection to the control board is properly connected.
There is one P60NF06 Mosfet, a Shottsky rectifier, 3 transistors S8050x2/S8550, and 1 78L05 regulater.
First check fet this way.
Disconnect motor terminal from fet output and connect a bulb of sam
Electronic Elementary Questions :: 22.08.2011 18:40 :: ALERTLINKS :: Replies: 39 :: Views: 2194
I've seen such gate drive circuits used when driving relatively large IGBTs over long leads (like over a foot of twisted pair). That's generally because of the problem you're referring to, with parasitic turn on of devices (which can happen to both low and high side switches). But if your driver circuit has a low impedance (...)
Power Electronics :: 02.10.2011 01:22 :: mtwieg :: Replies: 1 :: Views: 908
Hi - I'm trying to build a discrete low side fet driver. My plan is to use it to drive a fet as part of a fairly fast DC/DC boost converter (probably switching at 250KHz). Thus I'm looking to minimize rise and fall times on the gate of the fet.
Please see the attached LTSpice schematic and simulation (...)
Analog Circuit Design :: 04.10.2011 01:56 :: uoficowboy :: Replies: 17 :: Views: 807
I wish to use the HM42-40002LF gate drive transformer in a two transistor flyback converter at 67KHz
...however, the datasheet doesnt state the value.
I cannot understand how i am supposed to work out if it will saturate or not.
For my application, i require of T(sw)*12 = 180.
Power Electronics :: 13.12.2011 08:26 :: grizedale :: Replies: 1 :: Views: 401
it will just be a digital output where the load(realy most probably) will be driven using a fet for transistor.
the input supply will be from 24 to 60v but we have to implement a limit of .5A at 60V. at other voltages also shortcircuit protection must be there
Analog Circuit Design :: 15.12.2011 04:36 :: vishnupg :: Replies: 8 :: Views: 1680
You are only trying to generate 1 watt. Should be pretty easy to find a modern fet or Transistor that can easily put out that much current (i.e ~ 1 A rms) and do the frequency.
My point is if you have a < 1 ohm input impedance, don't use a 50 ohm output impedance amp--if for no other reason that you can not accurately measure the actual anten
RF, Microwave, Antennas and Optics :: 07.02.2012 07:55 :: biff44 :: Replies: 15 :: Views: 909
Consider using something like a quad NOR (parallel as many
as you like for drive - 74ACT02 - with the other input being
a RC network with C to 5V, R to GND forming a power-on
reset / holdoff. The natural state of the dormant uC + pullup
(1) will not energize the fet. There may be some elevated
Idd on the 5V-operated logic IC but ought to be toler
Analog Circuit Design :: 04.02.2012 13:18 :: dick_freebird :: Replies: 4 :: Views: 621
I'm new on this forum, and i'm hoping for your help!
I'm currently working on the design of an ultrasonic sensor. I'm using a 40kHz ultrasonic transceiver (both receive and transmit). The transceiver is driven by a transformer with 1:10 turn ratio. Parallel to the transducer i want to implement a variable resistor with high resis
Analog Circuit Design :: 20.02.2012 12:00 :: rbolijn :: Replies: 7 :: Views: 682
I would like to ask about cell balancing circuit.
This is the very simple balancing circuit for a first cell:
I can't test this circuit till I make a PCB.
Li-ion battery cells' voltage is 4.2. I'm using a microcontroller (3.3V) to drive this fet. fet is logic (...)
Analog Circuit Design :: 22.04.2012 07:18 :: Rokas :: Replies: 1 :: Views: 383
Are you trying to drive the fets directly with the optocoupler, or are the optocouplers driving other gate drive ICs? You should post the actual gate drive schematic.
Insufficient current in the isolators can cause several problems. Of most concern is the possibility that the turn off time of each fet (...)
Power Electronics :: 02.05.2012 08:16 :: mtwieg :: Replies: 13 :: Views: 1065
MOSfet's are pretty simple to operate as a switch. However it seems like to get the lowest Drain Source resistance the Gate voltage needs to be quite a bit higher than what most logic circuits can supply (in the range of 12V for Vgs). How would I do this using an NPN transistor between a Microcontroller and a MOSfet driver?
Microcontrollers :: 21.05.2012 14:34 :: 777funk :: Replies: 5 :: Views: 2369
Yes, you can do it. Will the mixer performance be "optimized"? Maybe not.
Specifically, the port to port leakage and the spurious signal levels (M x N products) may be different if you drive the IF port with the high power instead of the LO port. Sometimes the only way to tell is to actually test a unit.
Similarly, for some applications,
RF, Microwave, Antennas and Optics :: 27.06.2012 15:41 :: biff44 :: Replies: 6 :: Views: 357
The current limiter circuit forces the fet into linear operation. If the pulse energy dissipated by the fet before supply shutdown exceeds the SOA, the transistor will be damaged. As the capacitor is storing 9 Ws at 300 V, the transistor seems to be predestinated to damage.
You may want to clarify the exact control sequence and (...)
Power Electronics :: 04.10.2012 17:48 :: FvM :: Replies: 5 :: Views: 429
A PWM regulator LM2576, Lm2696 could be a solution.
Power Electronics :: 23.10.2012 17:33 :: ALERTLINKS :: Replies: 23 :: Views: 1186
I am building a battery switch using low side topology, see schematic below. MCU has control lines at logic levels, one to drive Q2 to allow load , the other to drive Q1 to allow charge. If I use logic level gate type Q2 MOSfet, I can drive it directly via MCU line. But I can't figure out how to (...)
Power Electronics :: 01.11.2012 08:19 :: electric1 :: Replies: 7 :: Views: 366
Hi dark night,
Look at it carefully, And you will see that when the uC outputs a HIGH, that causes the fet to conduct, which means node 3 is at GND potential. This causes the PNP BJT to conduct while at the same time the NPN BJT dosent conduct because the common emitter would be sitting at 0.7V above the base(node 3 which is GND) of the NPN BJT,
Professional Hardware and Electronics Design :: 14.11.2012 00:17 :: karthick1987 :: Replies: 2 :: Views: 364
Hello! I am biasing fet oscillator with three resistors. After choosing optimal load line and Q point I calculated Rd and Rs values. Additionaly put Rg resistor to "isolate" from voltage ground.
I use multimeter to measure Vgs and Vds. When i measure Vgs voltage, it is almost -0.6v (i need -0.3v). Then i discovered that have additional -0.3 vol
RF, Microwave, Antennas and Optics :: 09.12.2012 23:07 :: Terminator3 :: Replies: 10 :: Views: 534
Pls check these 2 links.
Analog Circuit Design :: 12.01.2013 12:21 :: mitz :: Replies: 10 :: Views: 260
It's not surprising that the simulation gives different results than reality. The simulation probably assumes not conduction losses in the passive components, and perfect gate drive for the fet.
You should at least try and verify that you're getting ZVS or ZCS when expected, so that your fet switching losses are low. Then you can start (...)
Power Electronics :: 16.02.2013 11:43 :: mtwieg :: Replies: 7 :: Views: 237
A few approaches are viable, such as using a resonant topology (LLC or phase shift bridge converter) or using better fet technology which mitigates the dissipation from hard switching (like GaN fets).
Power Electronics :: 21.02.2013 17:20 :: mtwieg :: Replies: 14 :: Views: 365
Hi unipolar motors are easy to drive the center taps of the coils go to the supply voltage. the coils can then be pulled to GND using a fet. you will need 4 fet's in total one for each coil. Don't for get to add diodes across the cols to help with back EMF from the switching. If you need more help let me know.
Microcontrollers :: 04.07.2013 20:19 :: markjbar :: Replies: 1 :: Views: 137
did find what looks like a single version of the OPA2690 you suggest.
This is the OPA690, until I saw that the input Impedance is too low by a factor of the order of 10.
The OPA2690 appears much the same.
Likewise for other 'possibles' which I looked at before starting this thread!
Thinking however that a suitable fet might be able to impeda
Analog Circuit Design :: 02.08.2013 13:15 :: audiomik :: Replies: 25 :: Views: 731