Turning on a MOSFET from 0-5V

[snip]

No.

The OP presented a ludicrous request, specifying the allowed components.

Note the glitch on the rising edge of my simulation.

I wouldn't do it that way at all.

But we have a pervasive trend in this group toward fewer components are better than "do it the right way"... obviously a leftist weenie conspiracy ;-)

...Jim Thompson

--
|  James E.Thompson, P.E.                           |    mens     |
|  Analog Innovations, Inc.                         |     et      |
|  Analog/Mixed-Signal ASIC\'s and Discrete Systems  |    manus    |
|  Phoenix, Arizona            Voice:(480)460-2350  |             |
|  E-mail Address at Website     Fax:(480)460-2142  |  Brass Rat  |
|       http://www.analog-innovations.com           |    1962     |
             
I love to cook with wine.      Sometimes I even put it in the food.

hmm, shot in the dark! a pull down resistor from the Gate to Ground to decharge the cap?

--
Real Programmers Do things like this.
http://webpages.charter.net/jamie_5

Can't you find a MOSFET that will be ON at 5V?

Tam

Hello Jim,

If it was then they'd demand more components. But all the transistors would have to be union members and if they don't get free health care and plum pensions these transistors would go on strike.

--
Regards, Joerg

http://www.analogconsultants.com

{:->

Turns out that the addition of 2x 1N4148 plus 1x resistor dramatically improves the translator.

...Jim Thompson

--
|  James E.Thompson, P.E.                           |    mens     |
|  Analog Innovations, Inc.                         |     et      |
|  Analog/Mixed-Signal ASIC\'s and Discrete Systems  |    manus    |
|  Phoenix, Arizona            Voice:(480)460-2350  |             |
|  E-mail Address at Website     Fax:(480)460-2142  |  Brass Rat  |
|       http://www.analog-innovations.com           |    1962     |
             
I love to cook with wine.      Sometimes I even put it in the food.

Hello Jim,

To avoid saturation?

--
Regards, Joerg

http://www.analogconsultants.com

Yep. Storage is a big deal in such a scheme.

Which thought provokes me to plug in a 2N2369 in place of the original

2N3904. Plus the two resistors, no diodes, looks great! Of course, gold-doped device doesn't store quite so much.

...Jim Thompson

--
|  James E.Thompson, P.E.                           |    mens     |
|  Analog Innovations, Inc.                         |     et      |
|  Analog/Mixed-Signal ASIC\'s and Discrete Systems  |    manus    |
|  Phoenix, Arizona            Voice:(480)460-2350  |             |
|  E-mail Address at Website     Fax:(480)460-2142  |  Brass Rat  |
|       http://www.analog-innovations.com           |    1962     |
             
I love to cook with wine.      Sometimes I even put it in the food.

Are you sure it takes 2 resistors and an NPN? In my world it takes 3 resistors :-). (two at the base - you want it between

0 and 5V while off, and one to pull the collector up to 12V). Nothing wrong helping a guy with his homework if one feels like it, btw - we all learn from what others have done before, a few of us sometimes do something worth being learned by those to come.

Dimiter

------------------------------------------------------ Dimiter Popoff Transgalactic Instruments

------------------------------------------------------

Jim Thomps> >

[snip]

NPN, gold-doped preferred, such as 2N2369

From collector, pull-up resistor to +12V (junction of collector and pull-up resistor is OUTPUT)

From base, pull-up resistor to +5V

Emitter, driven from output of CMOS logic device

Q.E.D ;-)

...Jim Thompson

--
|  James E.Thompson, P.E.                           |    mens     |
|  Analog Innovations, Inc.                         |     et      |
|  Analog/Mixed-Signal ASIC\'s and Discrete Systems  |    manus    |
|  Phoenix, Arizona            Voice:(480)460-2350  |             |
|  E-mail Address at Website     Fax:(480)460-2142  |  Brass Rat  |
|       http://www.analog-innovations.com           |    1962     |
             
I love to cook with wine.      Sometimes I even put it in the food.

--
Geez, thanks for the ad.

You only need one at the base if it\'s being driven by a totem pole,
and even if it isn\'t, the second one might work out as a noise
source.

Ah, expected that - but there is no 5V to be seen on the OP schematics.... This is a homework, remember :-). The 5V powered hc04 or whatever is on another board and you don't have a pin on the connector for them :-) :-)

Cheers,

Dimiter

------------------------------------------------------ Dimiter Popoff Transgalactic Instruments

------------------------------------------------------

Jim Thomps>

[snip]

Cheers, my ass. You're just making a feeble attempt to be difficult.

So locate NPN and base pull-up resistor on the board with the logic.

Collector of NPN thru connector to board with MOSFET and pull-up resistor to +12V ;-)

...Jim Thompson

--
|  James E.Thompson, P.E.                           |    mens     |
|  Analog Innovations, Inc.                         |     et      |
|  Analog/Mixed-Signal ASIC\'s and Discrete Systems  |    manus    |
|  Phoenix, Arizona            Voice:(480)460-2350  |             |
|  E-mail Address at Website     Fax:(480)460-2142  |  Brass Rat  |
|       http://www.analog-innovations.com           |    1962     |
             
I love to cook with wine.      Sometimes I even put it in the food.

--
Oops... missed the part about MOSFET...

Well, correct. Of course I was trying to be difficult, if I were not in the mood to talk I would be working and not discussing a homework.

Not that I would be cheerfully talking had I anticipated your hostility, (or was it that of your ass) but one keeps on learning.

Dimiter

------------------------------------------------------ Dimiter Popoff Transgalactic Instruments

------------------------------------------------------

Jim Thomps>

[snip]

On this side of the pond, "Cheers, my ass", is a poke at humor ;-)

...Jim Thompson

--
|  James E.Thompson, P.E.                           |    mens     |
|  Analog Innovations, Inc.                         |     et      |
|  Analog/Mixed-Signal ASIC\'s and Discrete Systems  |    manus    |
|  Phoenix, Arizona            Voice:(480)460-2350  |             |
|  E-mail Address at Website     Fax:(480)460-2142  |  Brass Rat  |
|       http://www.analog-innovations.com           |    1962     |
             
I love to cook with wine.      Sometimes I even put it in the food.

Oops, got misunderstood here... sorry. Lesson learned, though, although a bit different than I initially thought :-). On the positive side for me, I got back into my "working" mood.. :-).

Cheers,

Dimiter

Jim Thomps>

--
Wanna fight, asshole? 

OK, let\'s start with your "Transgalactic Instruments" crap.

How many shipments have you made to, let\'s say, even
extraterrestrial customers in our own galaxy?

Winfield Hill ha escrito:

Thanks Win. I wasn`t meaning to explain how the Gate should discharge, I guess that I`m accustomed to driving high current loads (realys, low impedance loads and such), the MOSFET took me by surprise. About the circuit:

I`ve studied ita long while, and I`ve determined the limiting factor for a higher voltage source is the NPN's Max Collector Power. The MOSFETs gate breakdown voltage shouldn`t matter because you`ll never put a voltage source that's inadequate for the output logic (in HIGH state) to handle. The BJT's C-E Breakdown voltage must inevitably be higher that the high voltage supply (for output LOW state). The resistor should be between the NPN's collector and the PNP's base, as shown:

VCC + | ------------------------| | | | .-. | | | | | | | | | .-. '-' | | | | |< | | Load ---------| '-' | |\\ | | | | .-. | | | | | | | | | | '-' | | | | | | | | | | ||-+ 0 or 5V Logic | | || | | | | | | | | | | | .-. .-. | | | | | | | | | | | '-' '-' | | | | ------------------------- | === GND The new R is 15k. All other Rs are 2.2k. 15k is as far as I would go without lowering the NPN's Emitter resistor R2.

This Resistor should prevent the NPN BJT to take all the remaining voltage: Vcc - 4.3V - 0.7V, thus reducing the power it dissipates, until the collector current reaches it`s maximum value and the transistor has to step up and take the remaining voltage. I`ve tested it with LTSpice up to 32V.

Well of course I might be wrong :)

Question: Is this the (Jim's) "way to do it" ? or this is how you do it with minimum parts, low cost and acceptable reliability ?

About the requirements: I thought they were acceptable, but that comes from inexperience, I know that I should know better, I`m learning everything I can.

[snip]

Thumb back thru previous posts. I described how to do it with one NPN and two resistors.

...Jim Thompson

--
|  James E.Thompson, P.E.                           |    mens     |
|  Analog Innovations, Inc.                         |     et      |
|  Analog/Mixed-Signal ASIC\'s and Discrete Systems  |    manus    |
|  Phoenix, Arizona            Voice:(480)460-2350  |             |
|  E-mail Address at Website     Fax:(480)460-2142  |  Brass Rat  |
|       http://www.analog-innovations.com           |    1962     |
             
I love to cook with wine.      Sometimes I even put it in the food.