hello everyone....

- first check the attachment please.....
- it is an inverter....
- 220 ohm resistors are connected from pins 10 & 11 to the gates of the mosfets...
- IC 4047 is given from a 12v supply.... so the output voltage pulse at 10 & 11 will be 12 (or less but not more...right)
- see the next attachment...the Vgs of IRF 540 is 20v...
if i give the 12v directly to the mosfet...then also it'll work in safe range
then what is the use of 220ohm....

 

The 220 ohm resistors prevent the Mosfets from oscillating at a VHF frequency due to their gate capacitance and inductance of their input wires. The 220 ohm resistors should be mounted as close as possible to the gate pins of the Mosfets.

 

thankyou audioguru...

how can i calculate the resistor value for different mosfets at different applications......

what parameters i have to concentrate.....???
any example.......please....
thankyou

 

Hi, try this; http://www.fairchildsemi.com/an/AB/AB-9.pdf

Cary

 

If you try to build that inverter, expect to blow up a number of MOSFETs.

I have a feeling that design will be prone to failure due to transformer "saturation walk".

http://www.google.com/search?hl=en&q=transformer+saturation+walk&aq=f&oq=&aqi=

 

thankyou shortbus.....
my doubt is cleared

 

If you try to build that inverter, expect to blow up a number of MOSFETs.

I have a feeling that design will be prone to failure due to transformer "saturation walk".

http://www.google.com/search?hl=en&q=transformer+saturation+walk&aq=f&oq=&aqi=

ok sgt...but iam not building that circuit......
my intension is to find the use of the gate resistor......
thankyou