Open the (mosfet) gate!

I believe the relevant graphs are on pages starting at 503. They only show currents up to 20 mA, but in nearly all cases that happens with just 1 volt on the I/O pin. So the current drawn reaching that point will be much more than 20 mA. If the curves were extrapolated I believe they would show currents of 100 mA or more to start when the output changes state with a 5 volt Vcc. This number would likely be more like 50 mA when running from 3.3 volt Vcc.

Rickman jumps without reading (as usual ;-). Since we're placing a "booster" between Arduino and MOSFET, we need that number for availability of drive _to_the_booster_. ...Jim Thompson

Here's a first pass...

...Jim Thompson

-- | James E.Thompson | mens | | Analog Innovations | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | STV, Queen Creek, AZ 85142 Skype: skypeanalog | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at

Thinking outside the box... producing elegant solutions.

"It is not in doing what you like, but in liking what you do that is the secret of happiness." -James Barrie

Change Q2 to 2N2369 to minimize storage delay...

...Jim Thompson

Wow! Thanks!

Just wondering, what are the diodes for? I also thought having two transistors would slow things down even more.

Much appreciated!

Michael

I first came up with that scheme for the MC1554 OpAmp in the mid '60's.

Study current flow when Q2 in fully on, versus when Q2 is off. ...Jim Thompson

When on, the diodes allow Q2 to drain current from the gate while turning off Q1. In essence the diodes allow the two transistors to act as a push-pull stage without the extra transistors needed to level shift the control signal. Q2 both does the level shifting for Q1 and drains the charge off of the M1 gate.

Currents displayed...

...Jim Thompson

Is PSpice better than LTSpice? Those are nifty graphs you have there.

Michael

Just a wee bit. But it's not free. When I first purchased it (late '80's) it cost me $8K, plus about $1500/year "maintenance". I've since discontinued maintenance since Cadence is intent on killing it as a tool useful for chip design, and started removing features. (Fortunately, at that time, PSpice was entirely .INI configured, so it was easy to fix Cadence's hatchet job.)

Yep. Chosen arbitrarily for illustration.

...Jim Thompson

This is horrifying.

mrdarrett.5gbfree.com/nasty.jpg

Michael

newer MOSGET design

Here's a hard working FET driver,

Seems like it would have been summoned for other uses, but I have not seen any circuits. Mikek

Other people make generic 442x series drivers. They are fierce enough to use alone in lots of cases.

And semiconductors only emit/drain when its closed.