is the output of a bipolar 555 large enough to drive a mosfet - Electronic Circuits Projects Diagrams Free

user1453 · 8th October 2006, 07:24 PM

as the title suggests, is the output of a 555 bipolar timer great enough to drive an irf740 n power mosfet.

the application is for a coil gun

do I need to addd an additional gate drive circuit?

audioguru · 8th October 2006, 07:59 PM

The IRF740 and most other Mosfets are spec'd to turn on fully with 10V on the gate. A 555 will give an output of 10V when its supply is 11.3V. Use a 12V supply and it will be fine.

An IRF740 is rated for a very high 400V but fairly low current. Is it useful to drive a coil?

Tarsil · 8th October 2006, 08:00 PM

About the curent.....no problem. About the voltage ...the treshold is like 4V max but at 10V RDS(on) is quite small so if u use like 12V for powering the 555...it's the best sol.

user1453 · 8th October 2006, 08:00 PM

pulse rated current is 40A

Styx · 8th October 2006, 08:27 PM

watch out for the output sourcing capability of the 555 timer w.r.t. how fast you want to switch the FET

audioguru · 8th October 2006, 08:31 PM

Quote:

Originally Posted by user1453

pulse rated current is 40A

That is the current when a very high supply voltage is used. Its minimum current is only 10A at lower voltages. Its on-resistance is high.
An ordinary IRF540 has a max on-resistance 10 times lower.

You can't buy exactly what you need, so plan on the worst case then all your circuits will work.

user1453 · 8th October 2006, 09:10 PM

however the voltage rating is 1/3rd of the irf740, this would bring the energy stored in the cap bank from 450j to 50j

audioguru · 9th October 2006, 03:42 AM

Does this powerful "coil gun" launch small cars?

user1453 · 9th October 2006, 09:10 PM

no, but small bits of steel at high speed

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8th October 2006, 07:24 PM	#1
user1453	is the output of a bipolar 555 large enough to drive a mosfet as the title suggests, is the output of a 555 bipolar timer great enough to drive an irf740 n power mosfet. the application is for a coil gun do I need to addd an additional gate drive circuit?

8th October 2006, 07:59 PM	#2
audioguru	The IRF740 and most other Mosfets are spec'd to turn on fully with 10V on the gate. A 555 will give an output of 10V when its supply is 11.3V. Use a 12V supply and it will be fine. An IRF740 is rated for a very high 400V but fairly low current. Is it useful to drive a coil? __________________ Uncle $crooge

8th October 2006, 08:00 PM	#3
Tarsil	About the curent.....no problem. About the voltage ...the treshold is like 4V max but at 10V RDS(on) is quite small so if u use like 12V for powering the 555...it's the best sol. __________________ If is too complicated.....most of the times is the wrong way.

8th October 2006, 08:27 PM	#5
Styx	watch out for the output sourcing capability of the 555 timer w.r.t. how fast you want to switch the FET __________________ Nothing is impossible. Once a problem is realised, the rest is just details

8th October 2006, 09:10 PM	#7
user1453	however the voltage rating is 1/3rd of the irf740, this would bring the energy stored in the cap bank from 450j to 50j

9th October 2006, 03:42 AM	#8
audioguru	Does this powerful "coil gun" launch small cars? __________________ Uncle $crooge

9th October 2006, 09:10 PM	#9
user1453	no, but small bits of steel at high speed