EMRFD Message Archive 3749

Message Date From Subject
3749 2009-11-08 09:23:39 WA0ITP PNP Switch
I'm looking for a pnp switching transistor, 500ma - 1A Ic in a TO-92 or TO-18
case.
I've been unable to locate one and wonder if one is actually available.

Has anyone on the list used one in this current range and physical size?

Thanx for any info.
-----------------------------
I love this radio stuff !
72, 73 Terry, WAØITP
www.wa0itp.com
www.4sqrp.com
www.qrpspots.com
3750 2009-11-08 09:38:23 Lasse Re: PNP Switch
Maybe the BC640 would work??
Ptot: 1 W
Polarity: PNP
Vceo: 80 V
Ic: 1 A
ft: 50 MHz
TO92

/Lasse
WA0ITP skrev:
> I'm looking for a pnp switching transistor, 500ma - 1A Ic in a TO-92 or TO-18
> case.
> I've been unable to locate one and wonder if one is actually available.
>
> Has anyone on the list used one in this current range and physical size?
>
> Thanx for any info.
> -----------------------------
> I love this radio stuff !
> 72, 73 Terry, WAØITP
> www.wa0itp.com
> www.4sqrp.com
> www.qrpspots.com
>
>
>
3751 2009-11-08 09:47:46 WA0ITP Re: PNP Switch
Excellent,

Thank you Lasse, appreciate the help..
-----------------------------
I love this radio stuff !
72, 73 Terry, WAØITP
www.wa0itp.com
www.4sqrp.com
www.qrpspots.com



----- Original Message -----
3752 2009-11-08 16:34:26 Harold Smith Re: PNP Switch
2N2907 is TO-18, and PN2907 or MPS2907 are TO92. They are the PNP
complements of the 2222 family, and are rated 600 mA continuous. The 2N4403
is similar, TO92, and also rated 600 mA. The MPS-A55 is rated 500 mA in a
TO92.

There are also a lot of similar but higher current transistors from Zetex in
TO92-like cases, and from NXP (formerly Philips) but NXP may have gotten rid
of its TO92 packages to concentrate on SMT parts.

You can also look at some of the Japanese parts. 2SA and 2SB parts are PNP,
and some are available in TO92, though usually with different pinouts than
most American TO92. Also with the Japanese transistors you'll want to
notice that their TO92 packages are usually rated for lower total power
dissipation, which is often not a factor in switching service.

Hope this helps.

de KE6TI, Harold

3753 2009-11-08 16:57:50 WA0ITP Re: PNP Switch
Thanx Harold, I appreciate the reply.

I had tried the 2N4403, but it became hot at 130 ma continous for 2 minutes. It
was saturated and had .2 volts across it, and since it got hot I was unsure of
it's acceptability as a switch.

I replaced it with at 2N3906 which stayed nearly at ambient for the same length
of time. Maybe the 4403 was defective.

I'm glad to know of the 2907s, I'll add them to the stash..

Thank you.

-------------------------
I love this radio stuff !
72, 73 Terry, WAØITP
www.wa0itp.com
www.4sqrp.com
www.qrpspots.com



----- Original Message -----
3760 2009-11-09 09:04:19 Tim Re: PNP Switch
3764 2009-11-11 15:48:56 popmedkoh Re: PNP Switch
Here's a thought. The transistors used in photoflash inverter circuits tend to have a very low saturation voltage combined with high gain and reasonable frequency response. They typically step up a single AA battery to more than 300 volts to charge up the photoflash capacitor, an application where you want to waste as little energy as possible heating up the transistor body. These devices have been used very successfully (significantly outperforming general purpose devices like the 2n3906, 2n2222 in "Joule Thieves" the circuits that suck every bit of power out of "dead" batteries to power LED torches. Best of all, they're free! Sort of...

Though the number of sources are drying up because of the dominance of digital photography, it's still possible to find friendly 1 hour photo places that will part with the spent single-use cameras especially if you explain that you will be salvaging parts to build amateur radio projects in a safe and ecologically friendly manner.

Now, what's the best camera to find? Most of the cameras have NPN output transistors. Lately however, Kodak has gone over to this circuit: http://repairfaq.cis.upenn.edu/sam/kflashmf.pdf where a cheap MOV replaces a pricier 110 volt zener diode. It also uses a PNP output transistor, a 2SA1585 in a TO92s package good for 3A though only 20 volts Vceo. Sometimes a 2SB1395 is used but as has been noted, the larger full size TO92 case doesn't imply higher specs: the Vceo is only 10 volts - fine for a single penlite supply but not great for practical ham applcations.

So how do you tell if the Kodak camera you've lucked up
3765 2009-11-11 16:12:40 WA0ITP Re: PNP Switch
Hi David,

Thanx vy much for the great info. I'll try "dumpster diving:" at our local
photo shops tomorrow.

-----------------------------
I love this radio stuff !
72, 73 Terry, WAØITP
www.wa0itp.com
www.4sqrp.com
www.qrpspots.com



----- Original Message -----