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31 Threads found on Fet Drive Circuit
The MOSfet with G=S=B=gnd! will change behavior if you try to drive the drain negative. Presuming the body diodes are well modeled, you will light up the D-B diode when you go much below ground. When you try to impose more current than the fet channel "wants", it has to go elsewhere (like into your shunt resistor). If you probe the (...)
I am testing this gate drive pulse transformer circuit but the top 2n2222 connected to positive rail runs hot the ground one runs cool should they not have used higher current transistors to drive s coil?. and should there not be a 1k resistor on its base as well as the other if anyone can help?. 131870
Hello, The attached shows a disastrous problem with a DC restored transformer fet gate drive. (shown here with a cascaded buck SMPS) ?when the converter is suddenly no-loaded from full load, the duty cycle obviously goes fairly quickly to zero. Ater the duty cycle has finally gone to zero, the fet gate voltage of the high side (...)
it looks ok but those bootstrap circuits can be bad if the fet vds transitions at more than 50v/ns....gate drive txfmr is better
even a good pnp struggles to get to 1A in 50nS... It should be noted that gate transformers with coupling factors in the supposed 0.9995 range have unconveniently high coupling capacitance, e.g. 100 pF, which is even worse for a fast switcher than a certain amount of leakage inductance. ...Thanks, these make m
How much more would it really cost to use a designed H-bridge driver IC to buffer the DFF's output up to reasonable sized fet gate loads? Or are you looking for a trivial output current on this project (claiming a DFF can drive a power fet, might be true in some sense for some size of fet, but liable to be (...)
Depends on how fast you want to switch the fet. Gate rise and fall times will suffer from Z-diode capacitance and relative high driver circuit impedance. An active pulse forming circuit, e.g. a CMOS gate or dedicated gate driver at the high side potential would be preferred. Average current consumption is (...)
You could even use the PV sensor to drive an NPN to disable a self biased Type N fet to switch the LED from the low side.
Hi, looking for help on my gate driver + fet circuit. The issue is that the node between the fets of the half-bridge drops to about -8V relative to the GND of my gate driver when the top fet turns off. I believe that this is largely due to the parasitic inductance of the (...)
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.
I don't see an initial drive on the fet gates?
You don't know, a priori, what "corner" affects a circuit's numerous performance dimensions. There are often competing interests such as drive vs leakage (and that's just one fet). This is why Monte Carlo is more interesting, even though it's a slow-motion pain in the nether sphincter.
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.
Hi... i want a switch of voltage rating 2KV and Td(on)<15ns, tr<15ns, Td(off)<15ns and tf<15ns.the switch can be either mosfet or bimosfet or IGBT. it is used for pulse modulator in jammer application. please if anyone knows or used these type of switch with these range let me hnow. thank you.
FVM is right, you have your circuit backwards. The drive to the fet should be your digital signal. The fet will short out the sine wave when it is ON, and will pass the sine wave when the fet is OFF. Also, to actually send data on the sine wave carrier, the sine wave frequency has to be much higher than (...)
Hi, In the attached figure, you can see that a P-fet (Power MOSfet) is to drive a big solenoid which operates at 8A constant current. A current sensing circuit and one or two filters on the line. one MOSfet driver is driving the P-fet (not shown in figure) at certain (...)
Simplest solution could be to use a N type fet with its drain pulled up(with the help of resistor) to VCC and source to ground. You can drive it gate with FG and get the output from drain. In this circuit your output will be inverted. Umesh
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 (...)
if I use a p-channel the Vgs voltage will be exceeded by the Voc of 22VThis seems to be a problem of the simple circuit you imagine rather than of the P-fet as such. There are always means to drive a suitable voltage to a MOSfet, independant of the converter toplogy.
Two comments: - You can't drive a NMOS-fet this way. It needs 5 to 10 V Vgs to turn it on. Switchers with NMOS output stage typically use a bootstrap circuit to drive the fet. Consult existing circuit examples. - A buck converter with unregulated PWM gives very poor output voltage (...)
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
Because unipolar pm2515-03 is restricted to medium speeds by design, any small power transistor (BJT, darlington or fet) can do, also integrated drivers.
I am trying to design my first circuit. The purpose is to drive 100 LEDs via PWM through four different channels on my PIC. The questions I have is can a PIC24FJ64GA002 drive 4 output channels with a PWM signal to drive a logic fet feeding strings of LEDs? The PIC specs can be found here:
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 (...)
Use a logic MOSfet switch or a semiconductor relay (photocoupler input).
Hi Pasicr, You actually did it the wrong way, you should have used 2N3906's to drive the anodes of the leds. You can change it but you gonna have to connect the emitters of the 2N3906's to the five volt supply and the collectors to the anodes of the leds AND add five base resistors to limit the base current. Don't forget to invert the output
in order to control devices such as motor, relay so on through pararell port, You must using driver because as you write, pararell port don't have enough current to drive such devices. you can choose between bipolar transistor and fet and design your own circuit based on your need to drive devices regards
i think your circuit will meet some problem, if your output voltage will not feedback to adjust the drive signal of the power mosfet
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 (...)
Hi, Im using this circuit as 20mA load. beacause of design specification i have to use OPA364. but this may not be able to supply 20mA. Im not sure , i can drive a fet to get desired op current. VDC=1.9 INV terminal = 0.9 V pls help me thanks ~niks~
pulse pwm use forinstance a 555 circuit too drive a fet on say a car you can pulse - 12v to the chasis and this will provent rust by making the gnd point lower this can be made relative too earth the sacrifice method is better although i take it it is iron or steel as you say rust not corrode or (...)