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Using Arduino => General Electronics => Topic started by: winner10920 on Oct 06, 2012, 04:32 am

Title: easiest way of driving amplifying from 5v to 12v
Post by: winner10920 on Oct 06, 2012, 04:32 am
What do you think would be the easiest, si plest way to turn a 5v signalinto a 12v signal? Im thinking either comparator with a 12 supply, or two npn transistors tho this doessnt seem as fast or energy effewcient
any other ways im not thinking of? It will basically be usedfor powering a mosfet so I need atleast 10-11 of my 12v supply, and its actually more important it turns off faster than it does on, so im thinking I may want to drive it low but idk which is best(btw its about 1000nc gate charge)
Title: Re: easiest way of driving amplifying from 5v to 12v
Post by: johnwasser on Oct 06, 2012, 07:02 am
An open-collector output and a pull-up resistor should convert 5V signal to 12V.  You can use an NPN transistor (and base resistor) to change your output to an open-collector output.
Title: Re: easiest way of driving amplifying from 5v to 12v
Post by: dhenry on Oct 06, 2012, 01:19 pm
Not sure what you meant by "amplify", but if you meant linear amplification, a cheapo LM386 will do.

For digital, get a npn.
Title: Re: easiest way of driving amplifying from 5v to 12v
Post by: Jack Christensen on Oct 06, 2012, 04:01 pm
Depending on the MOSFET being used, what it's driving, and the rise/fall time requirements (how fast it turns on and off), it may be possible to drive it directly with the 5V signal. One example: https://www.sparkfun.com/products/10618
Title: Re: easiest way of driving amplifying from 5v to 12v
Post by: winner10920 on Oct 06, 2012, 09:59 pm
Its a high voltge, high power type so definetly need 11 volts id say, what values would you use to achieve it? Because I want to drive it a little, but im not sure how strong a pull up down I an get without throwing off my gate voltage
Title: Re: easiest way of driving amplifying from 5v to 12v
Post by: Jack Christensen on Oct 06, 2012, 11:36 pm
Have a part number?
Title: Re: easiest way of driving amplifying from 5v to 12v
Post by: runaway_pancake on Oct 07, 2012, 12:18 am
It's pretty easy to use an NPN to switch the gate voltage.

See attached.
Title: Re: easiest way of driving amplifying from 5v to 12v
Post by: runaway_pancake on Oct 07, 2012, 12:33 am
If you need a "high-side" switch, and have an NPN and a PNP...
(http://i270.photobucket.com/albums/jj118/new_clear_days/circuits/hi-side_en.jpg)
With a 2N3904 and a 2N3906, it's good for at least 100mA, where Vout dips to 11.8V
Title: Re: easiest way of driving amplifying from 5v to 12v
Post by: winner10920 on Oct 07, 2012, 12:39 am
Im using this http://rohmfs.rohm.com/en/products/databook/datasheet/discrete/transistor/mosfet/r6010anx.pdf  (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
Title: Re: easiest way of driving amplifying from 5v to 12v
Post by: runaway_pancake on Oct 07, 2012, 12:52 am

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.
Title: Re: easiest way of driving amplifying from 5v to 12v
Post by: dhenry on Oct 07, 2012, 12:57 am
Quote
Its only drawback is that it needs an active HI to the NPN to turn the FET off.


If that's indeed a drawback, tie the 4.7k to 5v and put the arduino's otuput pin to the base of the npn. Turning arduino's pin as input turn on the npn. If you had pre-written a 0 to the pin, turning it into output turns off the npn.
Title: Re: easiest way of driving amplifying from 5v to 12v
Post by: runaway_pancake on Oct 07, 2012, 01:02 am

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


It's a comparator output, eh?
If it's one with an open-collector output then you won't need the NPN transistor/s.
Title: Re: easiest way of driving amplifying from 5v to 12v
Post by: winner10920 on Oct 07, 2012, 04:42 am
Not an open collector output,
however now imthinking about it I may go with another comparator to drive it because the ttotal part count is lower(1vs5), and while im pretty good at smd soldering I don't think I can make 5 of anysize components fit where a smd comparator could,
anyone have any good suggestions for a comparator that can handle a 12v supply and also drive a mosfet (maybe directly?) Or another simpler circuit?
Title: Re: easiest way of driving amplifying from 5v to 12v
Post by: Docedison on Oct 07, 2012, 05:49 am
Both the 3904 and 6 are good as switches to at least 50 Mhz... The Alpha cutoff is in excess of 150 MHz, I've used them as RF amplifiers in Commercial american business band radios (151 -159 MHz) with good success, A little noisy though at 150 MHz. I shouldn't think you will have any speed issues.

Bob
Title: Re: easiest way of driving amplifying from 5v to 12v
Post by: johnwasser on Oct 07, 2012, 03:32 pm

anyone have any good suggestions for a comparator that can handle a 12v supply and also drive a mosfet (maybe directly?) Or another simpler circuit?


Doesn't an op-amp with no feedback resistor act as a comparator?  The gain is high so if the + input is higher than the - input the output goes full high and vice-versa.  It shouldn't be hard to find a 6-pin op-amp package you can run at 12V.
Title: Re: easiest way of driving amplifying from 5v to 12v
Post by: dc42 on Oct 07, 2012, 07:37 pm
Why not use a proper mosfet driver IC such as TC4420 or TC4429? These will convert a logic signal from 5v to 12V and have good output drive in both directions.
Title: Re: easiest way of driving amplifying from 5v to 12v
Post by: winner10920 on Oct 07, 2012, 09:01 pm
Now that is perfect, exactly what im looking for in terms of size and functionality as well as simplicity
thank you
Title: Re: easiest way of driving amplifying from 5v to 12v
Post by: runaway_pancake on Oct 07, 2012, 10:34 pm
Well, if you're going to go shopping then why not get a logic-level FET?
How much current is the FET supposed to switch, anyway?
At first I thought this was about Arduino and using some IRF-type FETs you had on hand.
Then it turns out it was an about an op-amp (comparator).

[I'm not "annoyed", just asking questions.]
Title: Re: easiest way of driving amplifying from 5v to 12v
Post by: winner10920 on Oct 07, 2012, 10:49 pm
I am shopping around still, there is a 328p involved but its too busy to do the job of the comparator, I already decided on the mosfets for this project and bought those,(4 for an hbridge and one to turn the whole thing off entirely separate )
its more for incorporating into the design for my much larger project, I just was interested in finding the best wayfor my needs, I have 5v and 12v readily accessible I just didn't know the best(simplest) way to do it, using a dedicated driver that can be controlled from logic makes sense I just didn't think of even looking for something like that, I was first thinking of a non discrete way, but this definetly fits perfect
Title: Re: easiest way of driving amplifying from 5v to 12v
Post by: MarkT on Oct 08, 2012, 03:02 pm
If the signal to be amplified is AC only, then a transformer is a simple way to level shift, but won't give power-amplification.
Title: Re: easiest way of driving amplifying from 5v to 12v
Post by: arnster on Apr 13, 2013, 09:15 pm
I understand this post is old but for less than $5 digikey has exactly what you need
http://www.digikey.com/product-detail/en/VBT1-S5-S12-SMT-TR/102-1398-1-ND/989924
cheers