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Topic: easiest way of driving amplifying from 5v to 12v (Read 5 times) previous topic - next topic

Jack Christensen

MCP79411/12 RTC ... "One Million Ohms" ATtiny kit ... available at http://www.tindie.com/stores/JChristensen/

Runaway Pancake

It's pretty easy to use an NPN to switch the gate voltage.

See attached.
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Runaway Pancake

If you need a "high-side" switch, and have an NPN and a PNP...

With a 2N3904 and a 2N3906, it's good for at least 100mA, where Vout dips to 11.8V
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winner10920

Im using this http://rohmfs.rohm.com/en/products/databook/datasheet/discrete/transistor/mosfet/r6010anx.pdf and that last circuit I guess would work but wouldn't the vout be 11.3ish? Since the. 7v drop of the transistor? But now alos what would I do drive it low? A pulldown would waste energy and steal from the gate voltage as well
Turning it on idk if it takes 1ms to fully turn on but turning off id like to make as fast as possible
basically it will be receiving the output from a 5v comparator deciding whether it is on or off, id like to drive the mosfet in one step if possible but with the smallest footprint

Runaway Pancake

#9
Oct 07, 2012, 12:52 am Last Edit: Oct 07, 2012, 12:55 am by Runaway Pancake Reason: 1

that last circuit I guess would work but wouldn't the vout be 11.3ish? Since the. 7v drop of the transistor? But now alos what would I do drive it low? A pulldown would waste energy and steal from the gate voltage as well
Turning it on idk if it takes 1ms to fully turn on but turning off id like to make as fast as possible
basically it will be receiving the output from a 5v comparator deciding whether it is on or off, id like to drive the mosfet in one step if possible but with the smallest footprint



There's no 0.7V drop because it's all about Vsat.  
As I stated, at 100mA, that gets up to 0.2V.  Drawing less current results even less Vsat.
It's a tested circuit!
The PNP opens and closes the path to +V (12V), so its output is +V (less Vsat) when it's on or it's "open circuit" when it's off.
It's pretty fast.  The MOSFET switch time will have more to do with your Gate pull-down (and Gate capacitance).
A high from the Arduino output turns the NPN on, which takes the PNP base low, turning the PNP on, and enabling the final output.

The first circuit is the "easiest".  Its only drawback is that it needs a high to the NPN to turn the FET off.
"Hello, I must be going..."
"You gotta fight -- for your right -- to party!"
Don't react - Read.
"Who is like unto the beast? who is able to make war with him?"

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