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73 Threads found on edaboard.com: Mosfet Feedback
Hi. My understanding thus far is that in mosfet datasheets the maximum dv/dt is specified (generally as a number of volts per ns). I read somewhere that this applies to the rising of the voltage between the D and S (eg when the mosfet turns off). EG your actual rising edge signal must be slower than the spec to prevent mosfet failure. (...)
The Pmosfet is wrongly connected in your schematic. You should also consider that the mosfet booster circuit is adding gain and reducing phase margin so that the amplifier needs additional frequency compensation to achieve stability.
Hi all, I am trying to use a simple circuit to probe the VGS behavior of a subthreshold operating mosfet in temperature domain to validate the subthreshold models. I am trying to use either floating gate or gate-source connected mosfets to operate in subthreshold region in the entire temperature range (say 0C to 100C). I want to use the simulat
Hello I want to cancel the gate to source capacitance of one mosfet transistor in a circuit, I want a negative capacitance that put it parallel to gate-source, Is there any simple circuit just with mosfets that do this?
A common drain mosfet is a source-follower. It has no voltage gain and is extremely difficult to bias because if you make it push-pull the N-channel needs a fairly high input voltage and the P-channel needs a fairly low input voltage. A CD4007 or a CD4069 cannot be made to do what you want and if you use separate mosfets it will be very difficult.
I showed the circuit, I want make the amplifier with mosfet, but with greater gain than gmRo Consider gmRo an upper bound for the voltage gain. The idea simply doesn't work. Cascode topology is an option, as already mentioned.
Hi, I want to build a buck converter. I use the IR2113 gate driver but the voltage of VB and VS Ho, HL is zero. what is my problem. I think my connection it's not correct. 125502 thank you so much
it can work but a better way is to open a mosfet switch when Vbat reaches 13.8V using any accurate reference.
A mosfet inverts the input voltage if the input voltage is high enough to turn on the mosfet. For an N-channel mosfet a positive going input at the gate causes an output voltage at the drain to drop. Many mosfets have a threshold voltage (voltage from gate to source) of 2V to 4V for it to conduct (drain current) only (...)
Shorting Gate and Drain will bias the mosfet into a "diode" connection, Vgs=Vds ; i.e. there will be no gain between input and output. With a high resistance between drain & gate you can have gain.
Hi everyone, 115815115816 In the first picture, the circuit does not work when it is connected to the sbreak switch. In the second picture, the circuit works when it is connected to the gate driver (E) and the mosfet (IRF150), but the result goes wrong. I connected the upper dual flyback cir
Agree with comments from Klaus and schmitt trigger. My suggestion would be to use a P channel mosfet and for the voltage feedback have a resistor divider at node B itself. No need for opamp. The resistors values have to be in hundreds of k ohm to minimize the current consumption.
Alternatively/additionlally you could increase deadtime of the FETs. I think, it's the other way around. The regular way to prevent body diode conduction is to keep deadtime low and perform strictly synchronous switching. I agree that paralleled silicon diodes are mostly useless, doesn't matter if slow or fast. For low voltage
Actually, it could be as simple as this: 115771 It's a half-bridge design, so you could use any monolithic low-side/high-side mosfet driver (IR2110) and a cheap MCU/arduino to generate the PWM signal and to manage the output voltage feedback control. The mosfets are commonly used N-channel type.
the input of an opamp without feedback is infinite. Absolutely NOT for ordinary opamps that use bipolar transistors on their input. The input resistance of an old 741 opamp is a minimum of 300k ohms but is typically 2M ohms. Opamps with Jfet or mosfet input transistors have extremely high input resistance.
How to frame the drain current equation simply from the drain characteristics and transfer characteristics graph? Thank you.
What about DG1412 Ic instead simple mosfets.
I'm not sure what kind of stability is addressed here. If you look at feedback loop stability, the mosfet input capacitance can cause problems with high speed OPs and require additional compensation. Apart from this point, it's a well known and usually good working current source topology. mosfet power dissipation occurs according to (...)
Hamid you have very high gain in a design that compares current not power to the variable voltage. If you want to control dummy load power dissipation regardless of supply voltage, then you must monitor power. One way to monitor power is to mount a thermistor to the heatsink and use some anticipation or derivative feedback ( part of PID control) t
"...and the partial schematic i found on internet..." So, you started to build a circuit without having the full schematic? T5 (BF980 dual-gate mosfet) is the oscillator. This is ECO type oscillator (Electron Coupled Oscillator) using a tap on the inductor. If the tap is not in the right place, the oscillator cannot get enough feedback to oscillat
If transformer is fine, then there may be problem with the feedback circuit. I mean you can check by giving 3.3V from outside to your viper switch and check for 3.3V output if its coming correct and this will verify if everything including transformer and your switching of mosfet, is fine and then compare giving your actual feedback and (...)
The current and voltage are related, if your mosfet can't provide enough current then the voltage will drop. The constant voltage vs constant current don't have to do with the mosfet or the feedback signal type (DC, PWM etc) but with the feedback circuit itself. If the feedback circuit (we can call it a (...)
as for me I got to use mosfet. But facing problem using it. You realized that you can't drive the mosfet from ?C output without level conversion?
Hi its like boost converter, It will have a mosfet or BJT a high voltage switching device inside it and that will be clocked in a high frequency like 52khz, the switch will be connected series with a transformer on your need... The output duty cycle will depend on the feedback voltage.. And most of it will have a option like OFF/ON.. Look some typ
74HC595 has a maximum rating of 70 mA for GND and VCC terminals. This means, it can't drive more than 8.7 mA per LED if eight outputs are active. If the LEDs are operated in time multiplex, you'll most likely want more than 20 mA per LED, otherwise they would light rather dim. You don't need high current mosfet drivers to drive small 3A FETs.
hi all , i saw this curve in many books ,I knew in mosfet id=gm(vgs-vth),but when vds is falling , IL=(VIN-VDS)*t/L,IL=ID which should be rising ! so id should be constant or rising? the picture shows me it is constant ,why?:?: 96672
check your mains supply voltage. if its normal then check the mosfet mounting heatsink. their may be short in smps trafo.
Hello,I am repairing my DC-AC converter it was made up mainly by a high frequency transformer 12-0-12 which is connected to six mosfet controlled at 30KHz ,the second block of my device is made up by 4 power mosfet (which makes an H-Bridge),4 power diodes and the filtering block. An error has made then the output of my device has been connected
Hi everyone, i need some document for Analog components (Op-amp,transformer and mosfet) Placement guideline and Routing Guideline.if anybody have please share this post.what are factor i have to follow to reduce the EMI and EMC as well as Cross talk ??
If output depends only on transformer turns ratio, it means there are no feedback regulations in your simulation circuit. Primary wiring current ramps up until reaches comparator's (current sense) threshold causing mosfet transistor to turn off. Then voltage on the secondary wiring goes as high as turn ratio allows. Circuit is not controlled.
Hello, I'm building an accurate current limiter with limited amount of potential difference in voltage supply. I'm using a N-channel mosfet as driver and then having a NPN BJT to do feedback when current exceeds desired amount. Circuitry looks a bit like this: The problem is that
mosfets don't have any inherent slew rate. When you use them in a circuit, you may sometimes see slewing behavior, but that is a function of the rest of the circuit, not just the mosfet itself. With switching FETs, the only "slew rate" you'll really see mentioned is a max dv/dt on the drain, beyond which problems arise due to feedback (...)
Use a PWM controller such as MC34063, UC3845 or a specialized/dedicated boost controller to drive a mosfet in the regulator mosfet-inductor-diode based boost converter. Use a resistive divider based simple feedback circuitry along with the PWM controller to keep output voltage constant. The calculations involved should be easily obtained (...)
Regarding the design of the inverter, assuming that you're using a 50Hz transformer to step up, the stages are: PWM controller Power mosfet driver stage Power mosfet stage Output regulation / feedback stage Additional features - Battery low cut, overload protection, short-circuit protection, etc As for the PW
You should start with a small capacity inverter, like 100W. Then scale it up for your required power. Start learning on the various blocks - PWM control section, feedback section, mosfet drive section, power stage, output filter, etc. Two very common PWM controllers you could take a look at are SG3525 and SG3524. You can find lots of inverter-re
A few things - - A power FET meant for amps probably has a poorly spec'd, modeled and controlled leakage floor. - A VDMOS or LDMOS device is unlike a plain mosfet, it resembles more a mosfet with a cascode JFET at the drain. Its transition from linear to saturation will likely occur at lower drain voltage than you'd expect from MOS theory and ne
Have you studied the half-bridge topology? Where exactly are you stuck? Have you studied the various sections - oscillator, PWM, driver, mosfet bridge, transformer, output rectification, feedback, etc?
You should use a switching regulator to minimize losses. At 175W, you could use a PWM chip like UC384X or a microcontroller driving a mosfet in "buck" configuration. Then, use voltage feedback from the output to maintain a constant output voltage. The feedback loop should be adjusted as required. You could also use a ready made buck (...)
Hi all, this is probably blazingly obvious and just not adding up due to my lack of sleep but im working a switched transformer power supply. The mosfets are obviously on the primary side of the circuit but having the control ic's on the secondary side (with back up supply for power off situations) would make life a lot simpler:-D Will this work? b
Hi, I'm struggling with the aspect of internal capacitance of the mosfet, the pathway to remove the charge is required and thus I've added a resistor in parallel with the capacitor (colored in red) but I've no clue how to determine its size therefore would you be able to provide some feedback on that issue
66497 For example, in the Beta-Multiplier circuit I have attached here, when I sweep the VDD, the VSD of M4 increases at a higher rate than does the VGS of M2. Also, the gate of M3 follows VDD and keeps VSG constant. Why does this happen, Why is the gate-source voltage of a diode-connected transistor magically supply-inde
When you look into the source of mosfet, you have a resistance of 1/gm. So, here, we look into the source and hence have a 1/gm, Which comes in parallel with Rs. (refer eq 3.110. )
Hello, Will the bootstrap capacitor on this high and low side driver stay charged up when the full-bridge smps goes on no-load? NCP5181 The SMPS is:- Full-Bridge at 84KHz, Vin = 210VDC -373VDC Vout = +-40V Pout = 335W How much dummy loading will i have to add in order to
If you must put the limiter in the positive supply lead, using a PNP pass transistor can reduce the voltage drop well below 0.7V from collector to emitter. Using a mosfet instead of a BJT can get your voltage loss even lower. If you need real accurate voltage, run the feedback for your 10V regulator from the load side of the shunt and pass tran
Hi all, I am new to IC design. I am designing a sigma delta modulator for a very low frequency application of 20 Hz(its a bio sensor so it needs to be low power also). Which is the best continuous time filter to use. ( ladder type, Gm-C or mosfet-C ) or just a general amplifier with C in feedback. Thanks in advance.. Abhishek
Hi all, I am new to IC design. I am designing a sigma delta modulator for a very low frequency application of 20 Hz(its a bio sensor so it needs to be low power also). Which is the best continuous time filter to use. ( ladder type, Gm-C or mosfet-C ) or just a general amplifier with C in feedback. Thanks in advance.. Abhishek
After added feedback oscillator it started to oscillate. I don't want it. First comment, you don't necessarily need to cascade amplifiers, because the shunt has the same ground reference as the input signal. But with sufficient fast OPs, you possibly get stability problems due to the mosfet input capacitance even with a single OP.
i am trying to make a dc-dc converter from 9-12 Volt to 18 volt 4 amp my first trial was using a discerect comp. using 300 Khz but without feedback just constant load ( i was about to begin to make the feedback cir. ) the mosfet peak curr was about 10A and coil peak curr was about :10A now i said to use MC34063 since desing (...)
You didnt mention what type of inverter it is. Mean wether it is a transistor based one or mosfet based one?. Usually this problem is caused due to loose windings in the output transformer OR the feedback section which monitors the output OR the distorted waveform. Cheers
I am new to SMPS, I couldn't find any good articles that explain the feedback part of the flyback converter. From what I understand, the feedback controls the pulse width of the PWM driving the switching mosfet. If the load needs more current, the pulse width of the PWM just increases. Correct? I was wondering if there is any way of (...)