Post by thread:[OT] power transistor recomendation

I used to make a tip31 have more gain by driving it with a 2n2222 a little more circutry but cheaper than the hi-gain hi-power transistors. Just a thought, On Sat, 25 Jul 1998, Dwayne Reid wrote: {Quote hidden}> Hi! > > I'm looking for recomendations for TO-220 NPN and PNP transistors that have > moderate current gains at about 1 Amp. Should be good for at least 40V, hfe > greater than 100, reasonably robust. My old standbys TIP31, TIP32, TIP41, > TIP42 don't have enough gain and the TIP120 - TIP127 are darlingtons and > have too much voltage drop. I don't need complimentary pairs so unmatched > parts are fine. North American part numbers preferred. Any thoughts? > > Thanks! > > dwayne > > > Dwayne Reid <.....dwaynerKILLspam@spam@planet.eon.net> > Trinity Electronics Systems Ltd Edmonton, AB, CANADA > (403) 489-3199 voice (403) 487-6397 fax >

Take a look at BD435, 36, 37, 38, 39, 40, etc The Hfe is abaout what you need if iI remember correct For very low saturation and or *very high* gain take a look at Zetex Matrix transistors Otherwise consider another design and use MOSFET. Regards /Morgan At 19:41 1998-07-25 -0400, you wrote: {Quote hidden}>Hi! > >I'm looking for recomendations for TO-220 NPN and PNP transistors that have >moderate current gains at about 1 Amp. Should be good for at least 40V, hfe >greater than 100, reasonably robust. My old standbys TIP31, TIP32, TIP41, >TIP42 don't have enough gain and the TIP120 - TIP127 are darlingtons and >have too much voltage drop. I don't need complimentary pairs so unmatched >parts are fine. North American part numbers preferred. Any thoughts? > >Thanks! > >dwayne > > >Dwayne Reid <dwaynerKILLspamplanet.eon.net> >Trinity Electronics Systems Ltd Edmonton, AB, CANADA >(403) 489-3199 voice (403) 487-6397 fax > > / Morgan Olsson, MORGANS REGLERTEKNIK, SE-277 35 KIVIK, Sweden \ \ .....mrtKILLspam.....iname.com, ph: +46 (0)414 70741; fax +46 (0)414 70331 /

On Sat, 25 Jul 1998 19:41:02 -0400, you wrote: >Hi! > >I'm looking for recomendations for TO-220 NPN and PNP transistors that have >moderate current gains at about 1 Amp. Should be good for at least 40V, hfe >greater than 100, reasonably robust. My old standbys TIP31, TIP32, TIP41, >TIP42 don't have enough gain and the TIP120 - TIP127 are darlingtons and >have too much voltage drop. I don't need complimentary pairs so unmatched >parts are fine. North American part numbers preferred. Any thoughts? > >Thanks! > >dwayne > > >Dwayne Reid <EraseMEdwaynerspam_OUTTakeThisOuTplanet.eon.net> >Trinity Electronics Systems Ltd Edmonton, AB, CANADA >(403) 489-3199 voice (403) 487-6397 fax Not TO-220 (TO126), but I've used BUP40/BUP41 where I needed on/off switching with less loss than darlingtons. Fairly cheap and reasonable gain. If drop is a worry, any reason for not using Mosfets? ____ ____ _/ L_/ Mike Harrison / White Wing Logic / wwlspam_OUTnetcomuk.co.uk _/ L_/ _/ W_/ Hardware & Software design / PCB Design / Consultancy _/ W_/ /_W_/ Industrial / Computer Peripherals / Hazardous Area /_W_/

Thanks to all those who gave suggestions. Timothy Gray wrote: >I used to make a tip31 have more gain by driving it with a 2n2222 a little >more circutry but cheaper than the hi-gain hi-power transistors. Just a >thought, Thanks Timothy, but a darlington configuration has both too high a saturation voltage as well as too high Vbe turn on voltage for my application. Thanks for the suggestion, though. Tom McGahee wrote: >Have you considered using a Direct Coupled Compound (DCC) arrangement? This >has the gain advantage of a Darlington, but has only one forward >diode drop (Vbe drop). Thanks Tom. Yes, I had considered a compound transistor (thats what we call them here) but the saturation voltage was higher than I liked. Great suggestion though. I guess that I should mention what this is for. I'm trying to come up with a low dropout series pass device for a gell cell charger. My current designs use LM317 regulators as pass devices - these dropout at about 2.5V. They work great for line powered chargers (I've built LOTS of them) but are a problem when the charging supply comes down a very long data cable (part of my Pyro control system). Every volt of dropout that I eliminate adds several hundred feet of cable. The newest design has a pass transistor driven by a LM10. The whole thing vaguely emulates a LM317, except that the reference voltage is 0.2V instead of 1.2V. It would take a total redesign to use mosfets (I've been considering them, though). Thanks for all the suggestions. dwayne Dwayne Reid <@spam@dwaynerKILLspamplanet.eon.net> Trinity Electronics Systems Ltd Edmonton, AB, CANADA (403) 489-3199 voice (403) 487-6397 fax

A "Darlington" made with two discrete transistors need only have one Collector-Emitter drop for the load - the driver's collector is taken to + supply with a resistor rather than to the collector of the output transistor. Strictly speaking this is not a Darlington 9as I recall) but the result is the same. You still need a drive level of > 2 x Vbe drops to turn it on. Of course you can use *3* transistors to get a low turn on drive voltage, 1 CE saturation voltage. I won't try an ASCII picture. Drive small npn as usual. Collector drives base of a small signal pnp "hung" from top rail which turns on main output transistor. A few extra R's (and the extra transistor) are required. Depending on power level, switching speed required etc there is a slightly "dirty" method works well for appropriate cases. Turn output transistor ON with a pullup resistor from supply to base of sufficently low value to saturate it at desired full load current. Pull the output base down with a small signal npn (collector to output base, emitter to ground) which shunts the drive current when output is to be off. This gives an inverted drive polarity to normal and the pullup resistor needs to be able to handle the dissipation (which is probably OK in most cases and ...). I use this occasionally where appropriate and it works well. ---------- > From: Dwayne Reid <KILLspamdwaynerKILLspamPLANET.EON.NET> > To: RemoveMEPICLISTTakeThisOuTMITVMA.MIT.EDU > Subject: Re: [OT] power transistor recomendation > Date: Wednesday, 29 July 1998 07:14 > > Thanks to all those who gave suggestions. > > Timothy Gray wrote: > >I used to make a tip31 have more gain by driving it with a 2n2222 a little > >more circutry but cheaper than the hi-gain hi-power transistors. Just a > >thought, > > Thanks Timothy, but a darlington configuration has both too high a > saturation voltage as well as too high Vbe turn on voltage for my > application. Thanks for the suggestion, though. > > > Tom McGahee wrote: > >Have you considered using a Direct Coupled Compound (DCC) arrangement? This > >has the gain advantage of a Darlington, but has only one forward > >diode drop (Vbe drop). > > Thanks Tom. Yes, I had considered a compound transistor (thats what we call > them here) but the saturation voltage was higher than I liked. Great > suggestion though. > > I guess that I should mention what this is for. I'm trying to come up with > a low dropout series pass device for a gell cell charger. My current > designs use LM317 regulators as pass devices - these dropout at about 2.5V. > They work great for line powered chargers (I've built LOTS of them) but are > a problem when the charging supply comes down a very long data cable (part > of my Pyro control system). Every volt of dropout that I eliminate adds > several hundred feet of cable. > > The newest design has a pass transistor driven by a LM10. The whole thing > vaguely emulates a LM317, except that the reference voltage is 0.2V instead {Quote hidden}> of 1.2V. It would take a total redesign to use mosfets (I've been > considering them, though). > > Thanks for all the suggestions. > > dwayne > > > Dwayne Reid <spamBeGonedwaynerspamBeGoneplanet.eon.net> > Trinity Electronics Systems Ltd Edmonton, AB, CANADA > (403) 489-3199 voice (403) 487-6397 fax