hybridfree/eevblog-posts huggingface dataset:
More obscure Agilent parts: 1NB7-8539 mixer substitute  - Page 1
Forum section: electronics / projects

author: nexus
author_rank: Regular Contributor
timestamp: January 07, 2022, 03:09:28 am
content: Hi all,Back at it again looking for weird parts. This time, it is a suitable replacement for a 3-50 GHz active mixer, Agilent 1NB7-8539. This is used in the E4446/E4447/E4448A PSA spectrum analyzers with Option 123.https://www.keysight.com/my/partDetail/1NB7-8539Option 123 is the microwave preselector bypass. This adds the 1NB7-8539 mixer to the instrument, which can be switched into the input RF signal path using a transfer switch.This is needed to add the wide bandwidth digitizer options 122 or 140, since the signal path above 3 GHz is bandwidth limited and drifty as a result of the front end preselector filter.Now, no matter how much I bug Keysight they claim not to have the 1NB7-8539 available at all. It was only used in mmWave PSAs which are now obsoleted.At the end of the day, this is a mixer. There are other mixers out there. So there should be some other mixer I can add in place of this obscure, unobtainable Agilent branded one.The signal path for option 123 shows the input signal, up to +30dBm max between 3 and 50 GHz going into the RF port.The LO is between 3-7 GHz at 11 dBm.The IF is 321.4 MHz at -50dBm, which is the same as the standard signal path.Any suggestions for mixer options or considerations that I should take into account? I still consider myself an RF newbie; fixed a few instruments so far but I'm merely an EE master's student; I don't have grey beard wisdom quite yet.If any RF gurus out there have tips or tricks on how to approach this problem, I would appreciate the knowledge!Cheers

author: nexus
author_rank: Regular Contributor
timestamp: January 11, 2022, 03:46:49 pm
content: Been looking around online; so far, found the Marki M2-0250LNVT and M4-0150, which are passive double balanced and triple balanced mixers. Marki also has LO driver amps to match. Datasheets attached.More homework to do now, but off the bat for a spectrum analyzer front end (1st mixer), is either double balanced or triple balanced an obvious choice for this application?
more questions on triacs - Page 1
Forum section: electronics / projects

author: djacobow
author_rank: Super Contributor
timestamp: May 28, 2014, 11:23:53 pm
content: I've been experimenting with triac dimming circuits. I've built a few and they work, but I am seeing some complexity I do not fully understand.Let's take a look at the typical "hobbyist" dimmer circuit you'll find on the interwebz. It looks like this:This one was even kind enough to provide a snubber for managing the spike from inductive loads.But I've taken apart some real commercial wall dimmers and found that they don't look quite like this. In particular, they usually have a snubber, but just cap and no resistor, and they have an inductor in series, like this:(I stole this drawing from here:http://www.irf.com/technical-info/appnotes/an-1153.pdf)I guess the inductor is acting as a filter to keep all the EMI out of the AC system.So my questions are:- is the inductor just a low-grade EMI filter? My projects are actually boxed and a bit more complex than just a triac dimmer (multiple channels, uC control, blah blah) and actually have an IEC input with a mains filter. Can I go without the extra inductor then?- Why do the hobbyist circuits all leave it out?- What are the implications of the snubber without the resistor? Especially without the R to dampen things? The freq would be ~3/4 MHz.Anyway, taking apart commercial products has been instructive. They are /incredibly/ cheaply made, single sided boards, through hole, shoddy soldering. The triacs never have part numbers I can match to commercial parts. I can't seem to find inductors like the ones they use, either. I have a feeling they are custom.PS -- Bonus question! I've noticed that if I include a snubber circuit, say, with a 100 nF and 200 ohm resistor, then small loads, like phone chargers and even an aquarium air pump, will actually stay partially "on" even when the triac is off. The impedance of the RC network at 60 Hz is low enough that for a high impedance load, it continues to see a reasonably high voltage. This is interesting because in one of my projects I want to make a smart power strip that can control a bunch of arbitrary loads (no dimming). It seems like for this app, I can't make one circuit that would work for everything, at least not with a triac. I'm thinking of leaving out the snubber, since the triac won't be constantly hammered like in a dimmer, only very occasionally when it switches. But that seems 1/2 baked. Any ideas?
More than 2 coupled inductors in Ltspice, alternative model - Page 1
Forum section: electronics / projects

author: Etesla
author_rank: Regular Contributor
timestamp: June 24, 2024, 09:51:09 pm
content: Hi all.I want to model 3 coupled inductors (arbitrary self inductance, and arbitrary coupling coefficients between all three) using only coupling coefficients of 1. So I want to turn this:into a different circuit with 6 ports (for each end of each of the 3 inductors) using only coupling coefficients of 1. I do not know how to do that.I understand how to do this for 2 coupled inductors:Which is based on the description given in the LTSpice Wiki on transfomers:https://ltwiki.org/index.php?title=TransformersBut I can't translate that to three inductors. Mainly because, following the outline in that wiki page, I end up with a new 'L1' for each coupling statement involving L1I basically don't understand the math going on in the background when I create three inductors coupled with three K statements.How do I do this? What does the 6 terminal subcircuit look like that represents the same situation simulated with the 3 K statements in the first image?Thanks in advance!

author: Sensorcat
author_rank: Regular Contributor
timestamp: June 24, 2024, 10:07:43 pm
content: I'm not sure if I understand what you are trying to achieve, but a valid coupling statement for three inductors in LTspice would be:Code:K1 L1 L2 L3 1

author: Etesla
author_rank: Regular Contributor
timestamp: June 24, 2024, 10:32:33 pm
content: This is an example of a valid solution:but it's still not what I'm looking for because if my coupling coefficients get too big, my 'leakage' inductance for each inductor becomes negative...I can validate if a solution works or not by adding some other circuitry, and checking for example that the voltage across R3 and R7 are the same:
Morningstar PC Meterbus RJ11 Connections ? - Page 1
Forum section: electronics / projects

author: David_AVD
author_rank: Super Contributor
timestamp: October 08, 2012, 04:45:01 am
content: Has anyone played around with the Morningstar "Meterbus" (RJ11) connection on their solar charge controllers?A quick probe shows 3 pins connected to battery negative and two pins (connected together) with a reasonably "stiff" +14.5V (when 24V applied to battery terminals).The remaining terminal has +7.5V that looks to be a pull-up as it can be loaded down significantly with a 1K resistor. I assume this is the shared Rx and Tx line.There doesn't appear to be any data on this pin, but I suspect it will only reply when queried (slave mode).There is an adapter box/cable available, but not in Australia. Maybe someone here knows how the RJ11 interface works?
mosfet - Page 1
Forum section: electronics / projects

author: smokeiiot
author_rank: Newbie
timestamp: April 28, 2023, 07:21:44 am
content: hi all . im new here .i just wanted to ask a question on connecting a 60mA lamp to stm32 using a dual n channel mosfet . initally what we want is ,when turned on the lamp will be in high state for 30 sec. using pwm signal from PA8 of stm 32 it will be driven by a standalone 3 v output from a booster circuit. after 30 sec. the PA8 will go low and PA5 will be high and will be providing a .5 hz pulsing signal using another standalone 5v supply output from another booster. we would like to use FDC6561AN mosfet in this circuit . how can i connect this circuit.?

author: CountChocula
author_rank: Unknown
timestamp: April 28, 2023, 03:17:10 pm
content: Hiya! Assuming that the lamp doesn't need any current limiter (in which case you'd need an additional resistor), something like this might work:I assume here that the stm32 is operating at 3.3V, which isn't enough to drive the gate of the MOSFETs, so you need a couple transistors for that purpose. FWIW, you could just use any two jellybean NPN transistors in this circuit, and forego the MOSTFETs altogether.
MOSFET AC switch assistance - Page 1
Forum section: electronics / projects

author: grouchobyte
author_rank: Regular Contributor
timestamp: June 08, 2017, 11:27:20 pm
content: I am doing a project where I need to enable/disable the outputs of up to 20 transconductance (bipolar current cells) at +/-5 amps .... each in parallel or some combination with as few as 2 cells connected together, the rest being OFF or disconnected. I could use relays but that is bulky and takes up too much real-estate.Because the current cells use MOSFETs as the linear pass element, the body diode in a operating cell will not drive the load alone but will pass current into another cell that it is connected in parallel with and not outputting current or disabled.This transconductance topology used minimize the effects of interconnect inductance when operating at full AC bandwidth (1MHz) and very high currents up to 100A and load compliance to 8 VRMS or 23Vp-pTo make a long story short, I plan to overcome the body diode issue with back to back MOSFETs as an AC switch on the output of each current cell. Two, low RDSon N-CH MOSFETSs in a small SMT package should suffice. Something under 10 mOhms with Vds >30V, max Id>5A and not operating at speed, so gate charge and Cgs-Cgd do not matter. The switch would be either OFF or ON and not changed/switched dynamically. Kinda like a real slow load switch....What is important is low parts count or an integrated solution, possibly with two discrete or back to back MOSFETs, a floating charge pump and a logic level interface all "under one roof"Any suggestions are appreciated.@grouchobyte

author: grouchobyte
author_rank: Regular Contributor
timestamp: June 09, 2017, 01:56:45 am
content: I forgot to add that the cell power dissipation is moderated by envelope load sensing and compliance tracking so the input and thus the output of the current cell can range from 1 to 15 volts and thus the need for a floating pump to drive the back to back MOSFET gates.evb149......your comments are appreciated@grouchobyte

author: grouchobyte
author_rank: Regular Contributor
timestamp: June 09, 2017, 02:01:32 am
content: Quote from: evb149 on June 09, 2017, 01:57:35 amYup......see the previous post addendum

author: grouchobyte
author_rank: Regular Contributor
timestamp: June 09, 2017, 02:34:11 am
content: Thanks guys!All the usual suspects have checked in with suggestions and as expected your comments are helpful. I am a little surprised Tim W didn't jump all over this one 10 minutes after the OP, but maybe he had to get some coffee take a phone call or take a pee.@grouchobyte
MOSFET advice - Page 1
Forum section: electronics / projects

author: cthree
author_rank: Frequent Contributor
timestamp: May 30, 2013, 05:24:51 am
content: Anyone used a DMN2112SN N channel enhanced mode MOSFET? I'm looking to dim and switch power to a string of LEDs using PWM and an Arduino Mini. The LED strip is powered by a 12V 1A wall wort transformer. It seems capable and looks pretty fast. Other component options welcome.Any advice would be appreciated. I'd also like to add it to my inventory as a jelly bean part for driving small motors and such. Newark has them on sale.http://www.diodes.com/datasheets/ds30830.pdf

author: Kremmen
author_rank: Super Contributor
timestamp: May 30, 2013, 05:39:31 am
content: Offhand can't see any problems with that one. It should work OK. You might want to take a look at a similar component from the same mfg:http://www.digikey.com/product-detail/en/DMG6968U-7/DMG6968UDICT-ND/2052800. It has slightly better specs at essentially the same price. Id is 6.5A continuous, Rdson is 25 mohm (1/4 of DMN2112) and gate charge is also lower. This would indicate that the DMG6968 can handle bigger loads at higher frequencies.That said, if the DMN2112 is good enough then you need not look any further.

author: cthree
author_rank: Frequent Contributor
timestamp: May 30, 2013, 02:05:34 pm
content: Thanks for your feedback. Nice to have a second set of eyes.I chose that specific part because Newark has them on sale for $0.15 (CDN) vs $0.50 regular price (same price as the DMG6968 you recommend as an alternate). Since I have an order to place there and shipping is paid and I have a 15% off coupon I figured it would be smart to pick up a tube of 50 these for $7 to use for my project and to have at hand for others.I like to stock up on jelly bean parts when I can bundle them with other orders and especially if they are blowing out stock for 75% of regular price. It also helps to pad an order up to $200 for the free shipping, it's like getting parts for free
mosfet as a switch - Page 1
Forum section: electronics / projects

author: madhu.wesly01
author_rank: Regular Contributor
timestamp: December 12, 2018, 06:24:54 am
content: I'm implementing mosfet switching circuitry using the P channel enchancement mode mosfet DMP2305U.Where Vs = 3V and Vg is using as control voltage and toggleing between 0 and 3V . When Vg is zero volts , I'm getting output at Vd as high , when Vg is 3Volts I'm getting output at Vd as low as desired functionality, but i'm not getting the sufficient current through the mosfet . It seems like Vth of this mosfet is -0.9V and as a ground rule , Vgs should be greater than Vth to supply the max current , but here in my case Vgs is -3V (When the mosfet is on Vg=0v and Vs=3) .Here, do we need to consider the signs ?(negative , positive) of Vgs and Vth ?

author: David Hess
author_rank: Super Contributor
timestamp: December 12, 2018, 02:43:19 pm
content: As shown in your schematic, you are using the MOSFET backwards.

author: photomankc
author_rank: Contributor
timestamp: December 12, 2018, 02:58:05 pm
content: Yep, You have the symbol backwards to your text labels.In your example, assuming it's the right way around, then a 0V signal applied at the gate would give you about -3.0V Vgs and that should be sufficient to turn on and conduct significant current based on the datasheet curves. If you actually have it the right way around then we may need to see more of the real circuit to guess why it's not working fully.
Mosfet Avalanche in switching regulators - Page 1
Forum section: electronics / projects

author: Etesla
author_rank: Regular Contributor
timestamp: July 21, 2025, 05:09:06 pm
content: Hi all,I'm designing half bridges. There is a voltage spike on Vds on one of the two mosfets whenever that mosfet turns off. When the current that is being switched is high enough, that voltage spike can exceed the mosfets Vds rating for a couple 10's of nanoseconds, avalanching the mosfet.I have a very good understanding of where the voltage spike comes from (dI/dt and the loop inductance in the layout) and I have a very good understanding of the power dissipated in the mosfet during those avalanching events (no more than the energy stored in loop inductance (1/2*L*I^2) dissipated once every switching period). I have a very good understanding of the temperature implications of this extra power dissipation.I'm finding that I can actually optimize my overall mosfet losses by switching faster (reducing switching losses) and knowingly avalanching until my avalanche and switching losses combined are minimized. I am using very modern surface mount mosfets similar to this one: NTMFSC0D9N04CLAre there downsides to doing this? Does avalanching pose anything more than a thermal risk? Are there any oddball failure modes I should be wary of specific to avalanching with modern mosfets?I have read about 'hot carrier injection' but it's unclear what duration or mangnitude of current flow during avalanche is required for that to happen. It's also unclear to me if this is an issue for modern 'avalanche tested' 'rugged' mosfets.Thanks in advance mosfet experts!

author: xvr
author_rank: Frequent Contributor
timestamp: July 21, 2025, 10:05:44 pm
content: QuoteIt couild. For example - parasitic BJT latch up.https://www.infineon.com/assets/row/public/documents/24/42/infineon-applicationnote-some-key-facts-about-avalanche-applicationnotes-en.pdf

author: PCB.Wiz
author_rank: Super Contributor
timestamp: July 22, 2025, 02:46:50 am
content: Quote from: Etesla on July 21, 2025, 05:09:06 pmAnything the data specs as single pulse rated, I would be wary of using continually.Usually, a snubber or clamp is used to shift that power loss away from the FET.

author: Doctorandus_P
author_rank: Super Contributor
timestamp: July 22, 2025, 05:36:29 pm
content: Not all MOSfets are "avalanche rated". Maybe it's mostly "not tested", or maybe there other concerns. (latch up, hot spots, more?)Avalanche is usually a high energy event, so rating it in single pulse / Joules sounds logical to me. I assume that for multiple smaller avalanches, the total power dissipation is the main limit. Often there is also a graph that lists power handling for short pulses (small duty cycle).
MOSFET-based avalanche pulse generator - Page 1
Forum section: electronics / projects

author: cryptoprojects
author_rank: Newbie
timestamp: November 12, 2022, 05:36:43 pm
content: ...

author: Gyro
author_rank: Super Contributor
timestamp: November 12, 2022, 07:29:53 pm
content: I don't know if anyone has had any success with avalanching MOSFETs in this application, you could maybe try biasing the gate a bit higher but I don't know.People have had success avalanching other bipolar transistors, eg the (avalanche rated) FMMT413, but also the ZTX415, BSX20, and others, even the BC547...https://www.eevblog.com/forum/blog/eevblog-306-jim-williams-pulse-generator/msg127582/#msg127582

author: magic
author_rank: Super Contributor
timestamp: November 12, 2022, 09:30:53 pm
content: This circuit seems to rely on collector avalanche current entering the base layer, forward biasing the BE junction and effectively turning the BJT on for a moment to quickly conduct large current from the collector to the emitter at low voltage drop. I suspect that using the BC junction alone (or any other random diode) in the transistor's place wouldn't be nearly as effective.While MOSFETs also contain a parasitic NPN/PNP structure, the base and emitter (body and source) are shorted internally. Accidental triggering of the parasitic bipolar device can occur during avalanche or fast turn-off, resulting in prolonged conduction of current after turn-off, large power dissipation and destruction of the device. Every effort is made to disable this parasitic transistor, even under abnormal conditions.International Rectifier published full application note about avalanche ruggedness. It's the opposite of what you want to achieve.https://www.infineon.com/dgdl/an-1005.pdf?fileId=5546d462533600a401535590ab660f3a

author: David Hess
author_rank: Super Contributor
timestamp: November 12, 2022, 09:45:42 pm
content: Magic said what I was going to.Avalanche in a MOSFET happens with the parasitic collector-base junction which forms the body diode, and since the parasitic base-emitter junction is deliberately shorted, the amplification is not enough.Try other transistors, including RF transistors. Zetex even made a transistor specifically for avalanche operation, so try some of those "super e-line" transistors.
Mosfet Based Output Protection - Page 1
Forum section: electronics / projects

author: Rerouter
author_rank: Super Contributor
timestamp: April 23, 2017, 05:30:25 am
content: Currently resuming a long shelved project, and have thought up and simulated an idea that appear to work, but i figure i may as well run it by here first. as it feels too simple,I have to output a 5V supply (+-0.5V) of at least 1mA, into the world, the internal supply its fed from is 5V +- 0.02V, and the plug it connects to may be connected between hard + or -32V DC.(by hard i mean a direct unfused connection to a supply that can supply many amps, and cannot be crowbar'd)so far i have dreamed up the following, it looses about 0.35V across the schottkey, and 0.1V across the resistor, it's within my specs, limiting current when negative, and the diode blocking when positive, and as a bonus, disabling the output when the 5V internal supply is turned off,But i cant shake the feeling i have missed something obvious.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: April 23, 2017, 06:06:54 am
content: Why not use a single (0.5V) / (1mA) = 0.5k resistor?Tim

author: Rerouter
author_rank: Super Contributor
timestamp: April 23, 2017, 06:26:17 am
content: the negative extreme is 5V to -32V, so 37V, over 500 ohm would be 2.7W on the resistor, so likely a through hole 3.5W one for reliability, ($0.736 on digikey)with the limiting its 0.05W on the resistor and 0.7W on the mosfet, which is within the ballpark of the small package smd mosfets. (24c for mosfet + 3c for resistors + 44c for diode = $0.71 on digikey)It ends up with almost the same cost, just less heat lost, and (I believe) the perk of disconnecting when input power is lost.edit: (just rechecked my math, and the circuit limits at 20.5mA)

author: rx8pilot
author_rank: Super Contributor
timestamp: April 23, 2017, 07:32:56 am
content: Quote from: T3sl4co1l on April 23, 2017, 06:06:54 amI am trying to figure that out too.Sent from my horrible mobile....
MOSFET biasing with PMOS load - Page 1
Forum section: electronics / projects

author: shridmaster
author_rank: Contributor
timestamp: September 03, 2021, 02:33:09 pm
content: Not a homework problem, I'm refreshing before semester starts. Problem is from chapter 7 of Razavi Fundamentals. Given are Vth = 0.4V, un*Cox = 200uA/V^2, up*Cox = 100uA/V^2.Part a I figured out, Av = gm1 * (ro1//ro2), and ro1 and ro2 are 1/(lamba * Id). That gets me gm1, and I set gm1 = sqrt(2 * un*Cox * (W/L)1 * Id) and solve for (W/L)1. I got 7.8125.I'm now struggling on part b. The equation for bias Id of each transistor is 1/2u*Cox W/L * (VGS-VTH)^2 * (1 + lambda*VDS), both equal to each other (obviously using the PMOS version for the PFET)Where I'm having problems is how I go about finding VGS for M1 so that I can find VDS for M1, and where Vout is biased at (i.e what is VDS or VSD?). The drain-source voltage for M1 and M2 add up to VDD but that's all I know. I was going to assume Vout sits at VDD/2 but that seems wrong. Any pointers?

author: Zero999
author_rank: Super Contributor
timestamp: September 04, 2021, 08:14:20 pm
content: It's a class A amplifier. The MOSFETs are selected so the output and input voltages are half way between the supply rails.

author: magic
author_rank: Super Contributor
timestamp: September 05, 2021, 08:22:27 am
content: The FETs are designed, not selectedAnd Vin needs not be Vdd/2 and is irrelevant to the problem anyway.For the output you could start with Vdd/2, 0.5mA and also see if ro2 is low enough to make any difference.The truth is that the output can be anywhere, depending on feedback around M1.

author: shridmaster
author_rank: Contributor
timestamp: September 10, 2021, 04:03:35 pm
content: I'm noticing this a lot with MOSFET-based circuits, it seems like there's no simple closed form solution and you need to solve through iteration.Do I have that correct here? I should just pick a Vout and then iterate Vb until I get the correct value?

author: Zero999
author_rank: Super Contributor
timestamp: September 10, 2021, 06:18:21 pm
content: Normally there will be another large gain stage and a differential pair, so the gate voltages won't matter.

author: magic
author_rank: Super Contributor
timestamp: September 10, 2021, 06:49:33 pm
content: I have no clue about FET physics but I can do algebraIt looks to me like everything except Vds is given and you just need to solve the Id equation for Vgs.The problem is simply under-defined. Such an amplifier can obviously be made to work with just about any quiescent output voltage, and each voltage will require slightly different bias. So you just need to pick something, like Vdd/2, and go with it. Then the amplifier will have exactly 0.5mA bias current when operated at that chosen output voltage.

author: shridmaster
author_rank: Contributor
timestamp: September 10, 2021, 09:55:39 pm
content: Thank you all so much!!
MOSFET body diode as UFR diode - Page 1
Forum section: electronics / projects

author: electros6
author_rank: Regular Contributor
timestamp: September 22, 2017, 12:25:22 pm
content: Hi guys,I want to rectify 50KHz 100A output of a high frequency transformer for DIY welding machine. can I use body diode of the MOSFET for this purpose.regardsBaskaran

author: Circlotron
author_rank: Super Contributor
timestamp: September 22, 2017, 12:36:02 pm
content: With the body diodes on some mosfet I think you can get current crowding during the reverse recovery time. If you pop just one cell the whole die is dead. This was about 15 years ago. Maybe newer mosfet don’t have this trouble?

author: colorado.rob
author_rank: Frequent Contributor
timestamp: September 22, 2017, 12:36:34 pm
content: You tell us. What are the specs of the body diode? It is characterized in the datasheet.

author: cat87
author_rank: Regular Contributor
timestamp: September 22, 2017, 01:01:48 pm
content: It mainly depends on what frequency and switching conditions the MOSFETs work under. Though, best practice is to add discrete diodes, because the body diode tends to be kind of slow. Something like fast Schottkys would do in for most cases. Current requirements do not have to be the full 100A, because they only conduct part of the whole switching cycle. This should be calculated/simulated

author: technix
author_rank: Super Contributor
timestamp: September 22, 2017, 05:49:54 pm
content: What might your blocking voltage be?Will the 120A/45V STPS12045 work? That package contains two 60A diodes and you just need to wire them in parallel using bus bars to get the full 120A.

author: jmelson
author_rank: Super Contributor
timestamp: September 22, 2017, 07:00:33 pm
content: Quote from: electros6 on September 22, 2017, 12:25:22 pmUFR = ultra fast rectifier? Well, the body diode is an ultra SLOW rectifier! I did some testing, and found one particular large power fet would allow forward bias of up to 14 V for several microseconds before it started conducting! That blew out the gate driver chip. I had to add a real fast rectifier across the D-S to prevent that from happening.Don't trust the body diode to do anything useful for you.Jon

author: T3sl4co1l
author_rank: Super Contributor
timestamp: September 22, 2017, 07:26:53 pm
content: You'll be using the MOSFET as a synchronous rectifier, right? That's the preferred method, both for speed and losses.Tim

author: Wimberleytech
author_rank: Super Contributor
timestamp: September 22, 2017, 08:41:52 pm
content: I agree with jmelson.The body diode is a parasitic element that exists due to the structure of a MOSFET. Don't use it as a circuit element.
mosfet bridge rectifier, take two - Page 1
Forum section: electronics / projects

author: exe
author_rank: Unknown
timestamp: April 23, 2017, 09:57:00 pm
content: Hello my friends,I would like to know your opinion on this mosfet bridge rectifier. The "standard" approach is to use lt4320.But, after reading pretty much everything I could find on this topic, I decided to abandon lt4320 (which costs ~8euro in small quantities and barely available in Europe) and roll out this: (see attachment).Basically, it's a mix of two schemes: "ideal" diode using a mosfet mosfet bridge rectifier fromhttp://www.thetaeng.com/designIdeas/FETBridge.html.The result of mixing the two is in attachment.People often mention that P-channel fets have worse parameters and cost more, but don't really see a problem spending extra $1-2 for a one-off device. No noticeable performance degradation observed in the simulator, the key factors are Rds(ON) and Vg(th).The scheme should also work at lower than lt4320 voltages. Just be sure there is enough voltage to drive fets.So, looks like a real alternative to lt4320. Okay, it may be less robust and some tuning of resistors is necessary to ensure there is no (significant) reverse conduction, but looks to be working.Please tell me what you think. Is this a viable solution?

author: moffy
author_rank: Super Contributor
timestamp: April 26, 2017, 02:23:02 am
content: Unfortunately the reverse BE breakdown voltage on the transistors is between 5 and 6v. Spice doesn't simulate that.

author: digsys
author_rank: Unknown
timestamp: April 26, 2017, 03:17:22 am
content: The LT4320 does a heck of a lot more than just be a bridge. We use 100s of them, up to 30A. During my evaluation, I tried every trick in the book to try to fault them, but couldn't.Especially the critical timing from diode conduction (detection) > on state < reverse voltage (off) etc They are bust-proof. If you do go ahead with your design, test it well !,mainly Vop > Vip switching. I can't comment on your design, as this is one case you can't simulate.
Mosfet controlled Motor activates randomly - Page 1
Forum section: electronics / projects

author: fax8
author_rank: Contributor
timestamp: September 27, 2012, 03:49:26 pm
content: Hello guys, I'm designing a little project and I'm using a small Mosfet2N7002Pto drive on/off avibration motorfrom an ATMEGA 32u4.This is the relevant schematics and associate board layout:The problem I'm having is that, as long as the micro actively drives the gate to low or high, well.. everything work as expected.. instead when the micro is not driving the gate actively (high impedance) or when it's shut down (motor connected directly to the battery), the motor randomly activates.. sometimes just a simple vibration or touching with hands activate it.Battery is 1S Lypo 110mAh 3.7V nominal and the micro is running at 3.3V after an LDO.Is there anything I can do to prevent such effect? Maybe changing the gate resistor or adding one from the battery to the gate?Thanks for your help,Fabio

author: firewalker
author_rank: Super Contributor
timestamp: September 27, 2012, 04:03:17 pm
content: You shouldnothave the gate floating at any time.Notice the 100k resistor.Alexander.

author: fax8
author_rank: Contributor
timestamp: September 27, 2012, 04:15:26 pm
content: Thanks Alex. That makes perfect sense.. I wander what I was thinking...
MOSFET Designing Article - Page 1
Forum section: electronics / projects

author: kylehunter
author_rank: Regular Contributor
timestamp: February 26, 2020, 07:00:27 pm
content: Heya guys!I tend to stay over in the manufacturing and assembly forum, but figured I should spend some time elsewhere on hereI hope this type of post is allowed, if not, please let me know and I'll remove it! I do a lot of YouTube videos and post articles on my blog. Most are different personal projects or design topics or circuit reviews. I just posted my most recent one, which discusses some topics around designing for MOSFETs, specifically power MOSFETs.It seems that most articles or App notes out there are either super simplistic and overlook a lot of things, or in the case of App notes, are so complex with derivations that most people end up not being able to use them. I tried to stay in a bit of a middle ground here and focus on some equations, but making some simplifications to make it easier. I also have a related YouTube video that is also in the article on this topic as well.https://www.microtype.io/designing-power-mosfet-circuits/Please let me know what you think, or if you have any suggestions!
Mosfet Drain Source Resistance - Page 1
Forum section: electronics / projects

author: tazelikechickn
author_rank: Regular Contributor
timestamp: June 09, 2014, 10:58:28 pm
content: Hey Guys,I am trying to repair a SMPS out of a computer. I have found the Mosfet on the primary side is Kaput! Main problem is trying to get one the same. I have located a few that are similar, but I am unsure about the drain resistance. The Mosfet I have is a HD2N60 and I can get a similar one, but the drain resistance is different. the HD2N60 has 6 Ohms max and the one I am looking at (NDF02N60ZG) has a drain resistance of 4.8 Ohms. Is this enough to cause a problem?Cheers

author: TheRuler8510
author_rank: Regular Contributor
timestamp: June 09, 2014, 11:19:49 pm
content: I would bet that is no problem, but what about the other specs? IV curves, breakdown, threshold voltage, etc.At first glance I can't find a datasheet for HD2N60. I'll look again.

author: theatrus
author_rank: Frequent Contributor
timestamp: June 09, 2014, 11:25:54 pm
content: Things to watch out for:Often when RdsOn drops, the gate charge requirement goes up. If the power switcher can't drive the gate as fast it will dissipate quite a bit more power on each edge.Some driver setups use the RdsOn as an (imperfect but acceptable) current limit shunt.

author: tazelikechickn
author_rank: Regular Contributor
timestamp: June 10, 2014, 01:45:10 am
content: Hey Guys,Thanks for your replyHere is the data sheet for the HN2N60.http://www.alldatasheet.com/datasheet-pdf/pdf/18509/PHILIPS/PHD2N60E.htmland here is the one for the MOSFET I am looking at to replace it. (NDF02N60ZG) It is the closest specs I can findhttp://docs-asia.electrocomponents.com/webdocs/0edb/0900766b80edb286.pdfThey seem to compare OK apart from the drain resistance, which I don't know enough about.Cheers

author: TheRuler8510
author_rank: Regular Contributor
timestamp: June 10, 2014, 02:49:29 am
content: The spec I am most worried about is the threshold voltage. I think you may need to know a little more about how it is being used. If it is being driven high enough that there is margin in the current being switched, then it is not a problem. I would hope that it was designed with margin.Bottom line, maybe a problem, maybe not. Search Digikey for a better solution first--or just roll the dice and try it.Here are the IV plots from your datasheet, when gate voltage is X-volts, there drain currents are different:

author: TheRuler8510
author_rank: Regular Contributor
timestamp: June 10, 2014, 03:25:39 am
content: One more suggestion: Try it...Then measure the temperature of the MOSFET. As long as it is a reasonable temperature, and the power supply works, then I think you have an easy fix.

author: tazelikechickn
author_rank: Regular Contributor
timestamp: June 10, 2014, 04:35:41 am
content: Hey TheRuler8510,Thanks for your good advice. That's pretty much what I had in mind. Measure the temperature and that should tell if the resistance is an issue.It's all a learning curve!Cheers
Power error: Pump + Teensy 4.1 + MOSFET FQP30N06L + MOSFET Driver NCP81074 - Page 1
Forum section: electronics / projects

author: roboticsmick
author_rank: Newbie
timestamp: October 11, 2021, 03:43:31 am
content: Hi all, I was hoping to get some advice on how to switch on a pump using a teensy 4.1 + MOSFET FQP30N06L + MOSFET Driver NCP81074. I'm not sure where I am going wrong?When I power the 12V line on my schematic with a 5V source the gate turns on and the motor runs when I press the button on the Teensy, but when I swap the voltage source to a 7.4V or 12V battery the gate doesn't switch on? My schematics attached and my test code is below. Any advice on my error or where to do some research to fix my issue would be awesome and appreciated!FQP30N06L -https://cdn.sparkfun.com/datasheets/Components/General/FQP30N06L.pdfNCP81074 -https://www.onsemi.com/pdf/datasheet/ncp81074-d.pdfCode:#include <Bounce2.h>// Teensy 4.1#define PUMP_POWER_PIN 23#define PUMP_ON_BUTTON 30#define LED_TEST 2// Variablesint buttonDebounce = 5;// Button classBounce pumpSwitch = Bounce();// Pin Setupvoid setup() {pinMode(LED_TEST, OUTPUT);pinMode(PUMP_ON_BUTTON, INPUT);pumpSwitch.attach(PUMP_ON_BUTTON);pumpSwitch.interval(buttonDebounce);pinMode(PUMP_POWER_PIN, OUTPUT);digitalWriteFast(PUMP_POWER_PIN, LOW);}// Programvoid loop() {// Check if button pressedpumpSwitch.update();if (pumpSwitch.read()) {// Turn on pump and LED if presseddigitalWriteFast(LED_TEST, HIGH);digitalWriteFast(PUMP_POWER_PIN, HIGH);delay(100);// Turn off pump and LEDdigitalWriteFast(LED_TEST, LOW);digitalWriteFast(PUMP_POWER_PIN, LOW);}}Thanks in advance for any help!Cheers,Mick

author: maxiwaldi
author_rank: Newbie
timestamp: April 18, 2023, 11:55:01 am
content: Hi Mick,did you fix this Problem ?
MOSFET DS Leakage - Page 1
Forum section: electronics / projects

author: DerDaniel
author_rank: Contributor
timestamp: June 25, 2015, 12:26:13 pm
content: Hi,I'm new to this forum, but not new to electronics (studied it once in fact).I want to build a high precision PSU with switchable amp ranges. The shunt part shall look like one of those:Code:|o----o| || .-. |||-+ | | o--------o--------o||<- | |100R | | |-||-+ '-' ||-+ ||-+ ||-+| | ||<- ||<- ||<-o----o -||-+ -||-+ -||-+| | | | || .-. | | |||-+ | | .-. .-. .-.||<- | | 10R | | | | | |-||-+ '-' | | 1R | | 10R | |100R| | '-' '-' '-'o----o | | || o--------o--------o.-. || || | 1R'-'|Problem is the DS leakage of the MOSFETs when they are nonconducting. The PSUs max. ratings are 30V 3A so the FETs have to be able to handle that.All the MOSFETs I found have a typ. or max leakage of several to hundreds of uA. Not very good when there are 100R in parallel to measure nA.What made me curious is, that Dave and other guys use this system for amp range switching and seem to have no problem.So, are the datasheets massively overrated and in reality there are no such leakages?King regards--Daniel
mosfet for sd power management - Page 1
Forum section: electronics / projects

author: VIRNA CATTANI
author_rank: Newbie
timestamp: September 17, 2025, 08:54:53 am
content: I need to switch the power supply of an SD card connector. I’m considering using the DMP3085LSD-13 because of its low Rds(on). Since it’s a dual P-channel MOSFET, I was wondering: is it better to use both channels in parallel, or is it fine to just use one of them (if that’s possible)?

author: PGPG
author_rank: Frequent Contributor
timestamp: September 17, 2025, 10:55:48 am
content: I was using DMP2100U, but recently changed to DMP2045U.They both have:- smaller dimensions,- lower Rds(on),- ESD protected gate.
autoformer mishaps? - Page 1
Forum section: electronics / projects

author: SArepairman
author_rank: Frequent Contributor
timestamp: September 24, 2014, 02:06:26 am
content: so, has anyone melted anything by accidentally using an autoformer instead of a transformer?I managed to short out a few fuses doing this before. It took me a little while to figure it out. I had one in the junk box that had looked like a transformer, destined to act as an isolation transformer.Everything worked until I connected mains ground (for "safe mode" in a VARIAC).. and then poof. It took me a little while to figure it out, I was scratching my head for a bit wondering what the hell is going on.

author: TerraHertz
author_rank: Super Contributor
timestamp: September 24, 2014, 07:17:49 am
content: Quote from: SArepairman on September 24, 2014, 02:06:26 amOf those who did, some did not survive. The others may be too embarrassed to speak of it.QuoteUntil by chance you blew the breaker instead of dying.Personally, with mains transformers I check isolation with a meter before trusting them at all. And ever since I got a megger, by 'meter' I mean HV insulation tester.Edit: PS. I suggest you ask youtube to show you some 'death by electrocution' videos. Take it seriously.

author: SoundTech-LG
author_rank: Frequent Contributor
timestamp: October 08, 2014, 08:42:31 pm
content: I have a very, very nice one here. A em test V4780 S2. 16 amp 250 V rating. I assume it could easily be used at 120 V for 30 amps.But what could it be used for (besides the original intent)http://www.emtest.com/bindata/bindata/datasheets/data_sheet_V_4780s2_v102.pdf

author: David_AVD
author_rank: Super Contributor
timestamp: October 08, 2014, 09:32:12 pm
content: A wise move would be to check any transformer for connectivity between supposedly isolated windings, especially one that's unmarked or of unknown origin.
MOSFET gate driver - Page 1
Forum section: electronics / projects

author: electros6
author_rank: Regular Contributor
timestamp: November 29, 2013, 03:05:52 pm
content: hi guys ,I like to do my own power supply , I built is with precision in the prototype . I used simple transistor amplifier to boost 5V to 15V to drive the mosfet. I need yours suggestion about to amplify the 5V pulse signal of the microcontroller to 15V to drive the mosfet . I don't want any pulse transformer because I control the gate voltage of the mosfet to contol the power supply out so I want liner variation of my DAC output to be amplified to drive the MOSFET

author: dannyf
author_rank: Super Contributor
timestamp: November 29, 2013, 03:20:16 pm
content: QuoteMaybe you didn't realize this, but you already have it - as you said here:Quote

author: madires
author_rank: Super Contributor
timestamp: November 29, 2013, 03:31:20 pm
content: What about using a logic level MOSFET?

author: dannyf
author_rank: Super Contributor
timestamp: November 29, 2013, 03:38:07 pm
content: From what s/he wrote, s/he is not looking for a gate driver but actually a linear amplifier to drive the gate of a mosfet.

author: madires
author_rank: Super Contributor
timestamp: November 29, 2013, 03:50:05 pm
content: Quote from: dannyf on November 29, 2013, 03:38:07 pmAh, an OPamp in non-inverting configuration with a gain of 3. But the logic level MOSFET is still an alternative :-)

author: Zero999
author_rank: Super Contributor
timestamp: November 29, 2013, 05:57:17 pm
content: Quote from: electros6 on November 29, 2013, 03:05:52 pmWhy?Could you be using the wrong technology here?MOSFET drivers are typically switches, like a big logic gate with level shifting up to a higher voltage and higher current capability output. They don't take an analogue signal from a DAC and amplify it to between 0V and 15V. To do that, use a rail-to-rail op-amp configured as a non-inverting amplifier with a gain of 3. If you need a higher output current, you'll need to add a MOSFET to the output of the op-amp but within the feedback loop to boost the current.

author: dannyf
author_rank: Super Contributor
timestamp: November 29, 2013, 06:06:48 pm
content: QuoteDepends on what s/he was trying to do.QuoteSounds like it.

author: electros6
author_rank: Regular Contributor
timestamp: November 30, 2013, 02:38:36 am
content: using opamp to drive the mosfet , is it good , is it provide enough current to rice the mosfet

author: free_electron
author_rank: Super Contributor
timestamp: November 30, 2013, 03:06:44 am
content: Quote from: electros6 on November 29, 2013, 03:05:52 pmSCHEMATIC !pmos ? nmos ?if using an nmos you will need to be able to drive above the incoming rail.in any case you will need a current source or the thing will oscillate like hell.

author: calexanian
author_rank: Super Contributor
timestamp: November 30, 2013, 07:56:35 am
content: Oh heck! Just use an Ignitron to drive the fet.. Once.....

author: kg4arn
author_rank: Unknown
timestamp: December 01, 2013, 01:15:56 pm
content: Quote from: free_electron on November 30, 2013, 03:06:44 am@free_electron: Is this due to the gate capacitance of the MOSFET?
MOSFET gate voltage in this circuit - Page 1
Forum section: electronics / projects

author: XaviPacheco
author_rank: Regular Contributor
timestamp: September 05, 2019, 07:25:41 pm
content: The circuit attached below is from Texas Instruments:http://www.ti.com/tool/TIDA-00173My question is: what is the voltage at the gate of the MOSFET Q1? It is defined by the string of resistors R45, R42, R39, R36, R34 and R32, and the TVS diodes D16 and D15. But how do I calculate the exact value? I know the 12V zener across gate-source is for overvoltage protection.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: September 05, 2019, 07:46:06 pm
content: It's pulled down through D31 to ~12V (plus Vds of the first transistor) when turning on, and clamped at ~800V by D15-16 when off.Tim

author: XaviPacheco
author_rank: Regular Contributor
timestamp: September 05, 2019, 08:53:38 pm
content: The DC bus voltage ranges from 400V to 1200V, this means:For 400V, Iz = (400-12)/(470k*6) = 137.58 uAFor 1200V, Iz = (1200-12)/(470k*6) = 421.27 uAIz = Zener currentAren't these currents too low for the zener?
MOSFET H-Bridge Driver for +60V or -60V switching - Page 1
Forum section: electronics / projects

author: SujithADRF
author_rank: Newbie
timestamp: August 17, 2025, 11:19:23 pm
content: Hi,I am having a tough time trying to get LTSpice to simulate some MOSFET drivers in H-Bridge to switch +60V or -60V (based on input) to the load. Maybe someone here can help?I am attaching some pics that convey what I am trying to do: A diagram of what needs to be done & two LTSpice schematics that don't work!I am like. So hoping someone here may have an easy solution.Kind Regards,Sujith

author: PCB.Wiz
author_rank: Super Contributor
timestamp: August 18, 2025, 12:53:46 am
content: Quote from: SujithADRF on August 17, 2025, 11:19:23 pmNo surprise, that -60V is tough.You may need to use fully isolated gate drivers here, most mainstream parts are not designed to tolerate largenegativeshifts.

author: Zero999
author_rank: Super Contributor
timestamp: August 18, 2025, 09:11:19 pm
content: Yes, the negative voltage is a problem, but also the total supply voltage exceeds the maximum rating of both ICs.What's the duty cycle and maximum frequency range?Can't you use a couple of BJTs and a base drive transformer?

author: langwadt
author_rank: Super Contributor
timestamp: August 18, 2025, 09:46:17 pm
content: that driver is 60V max so that won't work, but ...reference a half bridge driver to -60V and isolate the input signals?

author: Zero999
author_rank: Super Contributor
timestamp: August 19, 2025, 09:37:19 pm
content: Perhaps the ADuM6132 will do?https://www.farnell.com/datasheets/1339844.pdf
MOSFET magically conducts (simple SPICE simulation) - Page 1
Forum section: electronics / projects

author: zphaze
author_rank: Contributor
timestamp: April 27, 2021, 08:17:37 pm
content: Hi,I simulated this circuit in MicroCap, a simple switch using a NMOS (NX138BK) and a PMOS.I get those results :Normally, I would expect VLOGIC to become 3.3V when VTRIG switches to 3.0V (0 -> 3V transition).The PMOS being high impedance, it should be to ground until the VTRIG applies a voltage at the gate which should then close the NMOS and thus close the PMOS so that 3.3V can appear at VLOGIC.Except it just doesn't happen. As soon as 3V3 starts (0 -> 3.3V), VLOGIC goes to 3.3V.Could someone rationally explain what is happening?And perhaps a solution?I tried different PMOS, but in vain (greyed out ones).I have attached the .cir file (MicroCap file). It is portable, thus the models are embedded in the file.

author: AlfBaz
author_rank: Super Contributor
timestamp: April 27, 2021, 09:12:11 pm
content: The drain and source seem to be mixed up on the nmos. This should allow the body diode to conduct, essentially you have a froward biased diode between 3.3 and vlogic

author: zphaze
author_rank: Contributor
timestamp: April 27, 2021, 09:28:38 pm
content: Quote from: AlfBaz on April 27, 2021, 09:12:11 pmThis doesn't look to be the case when checking in the component editor.

author: AlfBaz
author_rank: Super Contributor
timestamp: April 27, 2021, 10:06:56 pm
content: Check again 3v3 connects to source via 0 ohm resistor drain goes to earth via 47k resistor

author: xavier60
author_rank: Super Contributor
timestamp: April 27, 2021, 11:45:42 pm
content: It could be because of the effects of parasitic capacitance being simulated.

author: HackedFridgeMagnet
author_rank: Super Contributor
timestamp: April 28, 2021, 12:14:13 am
content: I think R38, R48, R47 needs a rethink. In reality it would depend on the nature and voltage of the Vtrig source. open collector, push pull etc.The voltage on the n channel gate should go between 0 and Vtrig. and Vtrig needs to be higher than the Vgs threshold which it certainly is.The p channel gate voltage is important but you haven't shown it. It is certainly not allowing the FET to turn off.Hope that helps.