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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
I think this option has more potential if you reduce the coupling capacitors and apply more damping. - - - Updated - - - Measurements on a breadboard test circuit also look promising. Trace one is the primary drive signal and lower trace measured on the gate of main fet.
Hello In the figure attached below if h Bridge is connected to isolated power supply of 300 volts will the high side mosfet work or not? (as voltage at gate must be around 10volts greater than the drain voltage and in isolated ground our bridge ground will be different so how boot strapping capacitor will get charge to provide 310 volts?) secondl
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 (...)
Hello, Do you have any improvements for the attached Pfet high side drive? The LTspice simulation is attached, plus schematic. The high side Pfet is getting turned ON/OFF at 20KHz.
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 should refer to the process design kit documents but generally the deviation of most basic parameters are within %10 to %20. But if you are asking how would a current reference should behave then I believe the answer is it should behave as a current reference for every corner. Depending on the application requirements it is possible that uA of
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.
You're not going to get those kinds of speeds from an IGBT and likely not a MOSfet either. Maybe you should think about doing your modulation at small signal rather than at high power.
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 (...)
Hi everybody I about to finish building my sine inverter with carrier frequency 2000hz and output voltage 110 v ac using PIC 16f877A now my problem is when I switch the N channel CMOS fet H bridge suddenly the circuit becomes very noisy and there is a short circuit on power supply. can anybody help me to overcome this short (...)
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:
I'm designing a mosfet based single phase inverter using h-bridge I'm using PIC controller to control the mosfets The problem is that even for low duty cycle pulses, the mosfet keeps conducting for a much longer period than it should and at high frequencies (close to 40Hz), one of the high side transistors starts heating up... so.. i (...)
Use a logic MOSfet switch or a semiconductor relay (photocoupler input).
drive the Display directly from the PIC outputs with no limiting resistors and no BJT or fet. PIC fet outputs are source self-limiting at 25ma. Connect the 8 Sink lines directly to PIC outputs also. For such a simple single LED Matrix circuit.... throw all the other components away! I have proven this setup with seve
you should try using a fet transistor switch, which can be controlled electronically... i cannot give you a detailed answer right now because i'm about to go to sleep and don't have my mind clear, but i will re-read this post tomorrow :D good luck anyways
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 (...)