What about input capacitance of gate which has to be charged and discharged and hence draw current. It is directly proportional to input frequency. For 50HZ, it is low. A gate resistance of 120 ohm will do. See datasheet Are you sure it is IRF8055.you have to calculate the needed gate voltage not the current
What about input capacitance of gate which has to be charged and discharged and hence draw current. It is directly proportional to input frequency. For 50HZ, it is low. A gate resistance of 120 ohm will do. See datasheet Are you sure it is IRF8055.
http://www.analogzone.com/pwrt1208.pdf
**broken link removed**
See gate charge,
http://www.irf.com/technical-info/appnotes/mosfet.pdf
Hello
MOSFET has a very high input impedance because the gate is isolated by the oxide, therefore the input current in the gate is assumed to be zero except for the leakage current which is small. it is right when you connect 8 transistors in parallel it will have more considerable value but still you have to think that the control of the MOS transistor is by voltage (Voltage controlled current device) not by current.
it mean you have to calculate the needed gate voltage not the current
You don't need current at the gate for all the frequency but you need to set an Voltage there so we go for drivers
Most FETs need 10-12V to switch on their gate. Microcontroller run with 5V. That is why a driver or level converter is used. There are logic level FETs which swtch with logic level (5V) and can be directly driven with MCU.
Can any body help to How can i Calculate MOSFET gate current if i use :
Totally 8 MOSFETs IRF8055 connected parrallely .
Frequency : 50Hz square wave.
Vgs=12V
so CAN I USE ANY TRANSISTOR TO DRIVE THIS GATE WHICH HAVE MAX: CURRENT CARRIYING CAPPACITY IS 500mA.
IF NOT Y?
You don't need current at the gate for all the frequency but you need to set an Voltage there so we go for drivers
How much MOSFET draws gate current depends on how fast do you want switch MOSFET.
Basic equation is Qtotal = I * tswitch. Qtotal you could find in datasheet.
From here you can see that if you need speed up MOSFET transient process you need increase gate current.
Main rule is higher switching speed means less dynamic power losses (In most cases)
That is not what I said. I meant that if you have less time on switching you have less dynamic power dissipation under the same frequencyhigh speed mean more dynamic power because the dynamic power is related to the frequency of operation that is limited by charging time of the capacitor which need more current to make it faster and hence more power
Can any body help to How can i Calculate MOSFET gate current if i use :
Totally 8 MOSFETs IRF8055 connected parrallely .
Frequency : 50Hz square wave.
Vgs=12V
so CAN I USE ANY TRANSISTOR TO DRIVE THIS GATE WHICH HAVE MAX: CURRENT CARRIYING CAPPACITY IS 500mA.
IF NOT Y?
We assume that you want the MOSFET to have minimal switching time - to limit the power dissipation. Yes ?
What you need is to find out the "Total Gate Charge' value from the spec-sheet. I could not find spec sheet for irf8055 ??
Then --
using gate charge you can easily calculate the amount of current required from the drive circuit to switch the device on in a desired length of time because Q = CV and I = C.dv/dt, the Q = Time x current. For example, a device with a gate charge of 20nC can be turned on in 20msec if 1ma is supplied to the gate or it can turn on in 20nsec if the gate current is increased to 1A.
These calculations would not have been possible with input capacitance values alone.
Conversely - if you have a limited current drive capability, then you can find out the fastest switching time you can achieve.
We use cookies and similar technologies for the following purposes:
Do you accept cookies and these technologies?
We use cookies and similar technologies for the following purposes:
Do you accept cookies and these technologies?