Recommend transistor?

[Satan's Little Sister]

I need a PNP transistor for switching 5 A/20 V at audio frequencies or
a bit higher. I've been through a dozen parametric searches and
downloaded scores of datasheets - there are too many candidates with
nearly identical characteristics, I can't try them all.

How do you go about picking the right power transistor? Anyone have a
favorite with a low Vce(sat) and a DC gain >30?

--
sls

 

[Leon Heller]

"Satan's Little Sister" <littlesisterNO@SPAMsofthome.net> wrote in message
news:udfho09d44jspsaoichr801kuu0b1os3tm@4ax.com...

I need a PNP transistor for switching 5 A/20 V at audio frequencies or
a bit higher. I've been through a dozen parametric searches and
downloaded scores of datasheets - there are too many candidates with
nearly identical characteristics, I can't try them all.

How do you go about picking the right power transistor? Anyone have a
favorite with a low Vce(sat) and a DC gain >30?

Why not just choose the cheapest one that meets your spec., is readily
available, has a SPICE model (in case you want to simulate your circuit),
and buy a couple. That's what most people do.

Leon

 

[Paul Burridge]

On Wed, 3 Nov 2004 11:43:13 -0000, "Leon Heller"
<leon_heller@hotmail.com> wrote:

"Satan's Little Sister" <littlesisterNO@SPAMsofthome.net> wrote in message
news:udfho09d44jspsaoichr801kuu0b1os3tm@4ax.com...
I need a PNP transistor for switching 5 A/20 V at audio frequencies or
a bit higher. I've been through a dozen parametric searches and
downloaded scores of datasheets - there are too many candidates with
nearly identical characteristics, I can't try them all.

How do you go about picking the right power transistor? Anyone have a
favorite with a low Vce(sat) and a DC gain >30?

Why not just choose the cheapest one that meets your spec., is readily
available, has a SPICE model (in case you want to simulate your circuit),
and buy a couple. That's what most people do.

Sounds like a BD132 might fit the bill.
--

"What is now proved was once only imagin'd." - William Blake, 1793.

 

[Rich Grise]

On Wed, 03 Nov 2004 11:25:52 +0000, Satan's Little Sister wrote:

I need a PNP transistor for switching 5 A/20 V at audio frequencies or
a bit higher. I've been through a dozen parametric searches and
downloaded scores of datasheets - there are too many candidates with
nearly identical characteristics, I can't try them all.

How do you go about picking the right power transistor?

Maximize/minimize the "important" paramaters, then go for price and
availability.

Anyone have a
favorite with a low Vce(sat) and a DC gain >30?

http://www.onsemi.com/site/products/parametrics/0,4446,798,00.html

Cheers!
Rich

 

[Clarence]

"Ban" <bansuri@web.de> wrote in message
news:Ax9id.257024$35.11983216@news4.tin.it...

Clarence wrote:
I need a PNP transistor for switching 5 A/20 V at audio frequencies
or a bit higher. I've been through a dozen parametric searches and
downloaded scores of datasheets - there are too many candidates with
nearly identical characteristics, I can't try them all.

How do you go about picking the right power transistor? Anyone have
a favorite with a low Vce(sat) and a DC gain >30?

You cannot switch AC with a bipolar junction transistor, it has a
built-in diode function, that will rectify and induce a horrible
distortion. However you can try two Mosfets in series, because they
have a parasitic diode from drain to source. But best will still be
a relais, and that is what is done normally.

If it is pulsed DC then you can do what you want. Have a look at
switching times too, because BJT tend to be pretty slow. They will
need a lot of current drive to achieve low Vce, so a good driver
stage is a must.
If the transistors have almost identical data, they will also behave
similar, so probably all of your candidates will work nicely.
Please be a little more specific about what you want to do, you will
get better advise then.
--
Ban

She said nothing about switching AC.
"switching 5 A/20 V at audio frequencies "
Is still a DC signal.
The level is 20Volts. The rate is "Audio frequencies."

How do you know? To me 5A/20V sounds more like the output of an audio power
amp with 100W into 4 Ohms, but if it is supposed to be a switched power
supply or something similar you might be right. A low Vce_sat supports your
understanding. That is why I wrote the last sentence above.
The transistors for both applications might be quite dissimilar, in fact.
--
ciao Ban
Bordighera, Italy

Well I "Know: because I read English.
What it "Sounds like" is that you didn't get it.
All audio Amps operate with DC, even "Class 'D'"

If you didn't know why didn't you just ask?

 

[Paul Burridge]

On Wed, 03 Nov 2004 18:53:48 GMT, "Clarence" <no@No.com> wrote:

Well I "Know: because I read English.
What it "Sounds like" is that you didn't get it.
All audio Amps operate with DC, even "Class 'D'"

If you didn't know why didn't you just ask?

We have to make allowances for these unfortunate dipshits who don't
have English as a first language. Ban's one of them. He obviously
doesn't understand the concept of an audio signal riding on a DC bias.
Or class B audio either, presumably. Still, no matter...

--

"What is now proved was once only imagin'd." - William Blake, 1793.

 

[Paul Burridge]

On Wed, 03 Nov 2004 18:05:47 -0500, Spehro Pefhany
<speffSNIP@interlogDOTyou.knowwhat> wrote:

On Wed, 03 Nov 2004 11:25:52 GMT, the renowned Satan's Little Sister
littlesisterNO@SPAMsofthome.net> wrote:

I need a PNP transistor for switching 5 A/20 V at audio frequencies or
a bit higher. I've been through a dozen parametric searches and
downloaded scores of datasheets - there are too many candidates with
nearly identical characteristics, I can't try them all.

How do you go about picking the right power transistor? Anyone have a
favorite with a low Vce(sat) and a DC gain >30?

For that current and voltage it might be better to use a power MOSFET.

However, if you want to stick with bipolar, maybe the ON MJD45H11
(0.36 in 1K). It's an ON "preferred device".

What? You mean it's hard to switch OFF? ;-)

(NB: see "latch-up" in CMOS devices)
--

"What is now proved was once only imagin'd." - William Blake, 1793.

 

[me]

How do you go about picking the right power transistor? Anyone have a
favorite with a low Vce(sat) and a DC gain >30?

I ususally just use one that works out of my junk box stock. You might
consider a higher DC gain depending on what you are driving the transistor
with. Maybe a darlington or two transistors hooked as darlington...


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[Ban]

Clarence wrote:

I need a PNP transistor for switching 5 A/20 V at audio frequencies
or a bit higher. I've been through a dozen parametric searches and
downloaded scores of datasheets - there are too many candidates with
nearly identical characteristics, I can't try them all.

How do you go about picking the right power transistor? Anyone have
a favorite with a low Vce(sat) and a DC gain >30?

You cannot switch AC with a bipolar junction transistor, it has a
built-in diode function, that will rectify and induce a horrible
distortion. However you can try two Mosfets in series, because they
have a parasitic diode from drain to source. But best will still be
a relais, and that is what is done normally.

If it is pulsed DC then you can do what you want. Have a look at
switching times too, because BJT tend to be pretty slow. They will
need a lot of current drive to achieve low Vce, so a good driver
stage is a must.
If the transistors have almost identical data, they will also behave
similar, so probably all of your candidates will work nicely.
Please be a little more specific about what you want to do, you will
get better advise then.
--
Ban

She said nothing about switching AC.
"switching 5 A/20 V at audio frequencies "
Is still a DC signal.
The level is 20Volts. The rate is "Audio frequencies."

How do you know? To me 5A/20V sounds more like the output of an audio power
amp with 100W into 4 Ohms, but if it is supposed to be a switched power
supply or something similar you might be right. A low Vce_sat supports your
understanding. That is why I wrote the last sentence above.
The transistors for both applications might be quite dissimilar, in fact.
--
ciao Ban
Bordighera, Italy

 

[Ross Herbert]

On Wed, 03 Nov 2004 11:25:52 GMT, Satan's Little Sister
<littlesisterNO@SPAMsofthome.net> wrote:

I need a PNP transistor for switching 5 A/20 V at audio frequencies or
a bit higher. I've been through a dozen parametric searches and
downloaded scores of datasheets - there are too many candidates with
nearly identical characteristics, I can't try them all.

How do you go about picking the right power transistor? Anyone have a
favorite with a low Vce(sat) and a DC gain >30?

Why not ask "how long is a piece of string?" You'd get the same
answer. You don't specify how much space is available because this
determines the mounting and heatsinking arrangement. There are
literally hundreds of candidates in all different packages but unless
you know the space requirements you can't start to make a choice.

 

[Rich Grise]

On Fri, 25 Mar 2005 10:01:55 +0000, Ross Herbert wrote:

On Wed, 03 Nov 2004 11:25:52 GMT, Satan's Little Sister
littlesisterNO@SPAMsofthome.net> wrote:

I need a PNP transistor for switching 5 A/20 V at audio frequencies or
a bit higher. I've been through a dozen parametric searches and
downloaded scores of datasheets - there are too many candidates with
nearly identical characteristics, I can't try them all.

How do you go about picking the right power transistor? Anyone have a
favorite with a low Vce(sat) and a DC gain >30?


Why not ask "how long is a piece of string?" You'd get the same
answer. You don't specify how much space is available because this
determines the mounting and heatsinking arrangement. There are
literally hundreds of candidates in all different packages but unless
you know the space requirements you can't start to make a choice.

2N3055. ;-)

Cheers!
Rich

 

[Ken Smith]

In article <pan.2005.03.25.17.36.04.790975@example.net>,
Rich Grise <richgrise@example.net> wrote:

On Fri, 25 Mar 2005 10:01:55 +0000, Ross Herbert wrote:

On Wed, 03 Nov 2004 11:25:52 GMT, Satan's Little Sister
littlesisterNO@SPAMsofthome.net> wrote:

I need a PNP transistor for switching 5 A/20 V at audio frequencies or
a bit higher. I've been through a dozen parametric searches and
downloaded scores of datasheets - there are too many candidates with
nearly identical characteristics, I can't try them all.

How do you go about picking the right power transistor? Anyone have a
favorite with a low Vce(sat) and a DC gain >30?


Why not ask "how long is a piece of string?" You'd get the same
answer. You don't specify how much space is available because this
determines the mounting and heatsinking arrangement. There are
literally hundreds of candidates in all different packages but unless
you know the space requirements you can't start to make a choice.

2N3055. ;-)

Thats an NPN, but it would make a good driver for a TIP-36.


--
--
kensmith@rahul.net forging knowledge

 

[Rich Grise]

On Fri, 25 Mar 2005 12:40:27 -0800, Glenn Gundlach wrote:

Rich Grise wrote:

2N3055. ;-)

Cheers!
Rich

Hey Rich, when did a 2N3055 become PNP ?
GG

Oops. Guess I missed that part. MJ2955 then. (or is that MJE?)

Cheers!
Rich

 

[Winfield Hill]

Rich Grise wrote...

Oops. Guess I missed that part. MJ2955 then. (or is that MJE?)

Depends if you want the metal TO-3 or the plastic version. But there
are much better choices than those old poor-performance transistors.
Is that why you put up the smiley? Very well, give us an alternate.


--
Thanks,
- Win

 

[Pooh Bear]

Rich Grise wrote:

On Fri, 25 Mar 2005 17:08:04 -0800, Winfield Hill wrote:

Rich Grise wrote...

Oops. Guess I missed that part. MJ2955 then. (or is that MJE?)

Depends if you want the metal TO-3 or the plastic version. But there
are much better choices than those old poor-performance transistors.
Is that why you put up the smiley? Very well, give us an alternate.

As OP said, there are billions and billions of them.

I was going by the term "favorites", which reminded me of the days as
a Radio Shack repair technician: The shop's entire budget was covered by
warranty repairs, mostly high-end stereos with blown output trannies, and
quasi-comp-sym was so common, that on my first one of these, the boss
said, "Just use 3055's." So 2N3055 was our first choice for replacement
output trannies.

brag
When I started there, they had about a 3-month backlog, and kept telling
customers, "It's waiting for parts". There were two other techs plus me,
and the boss, who worked occasionally. I practically single-handedly
cleaned up the backlog in about three weeks.
/brag

I know there are sh!t-hot complementary trannies now, but as for
recommendations, all I can say is, start from the spec, and pick
and choose based on ranges of parameters to narrow down the range
of choices, and then go by price and availability.

But heck, if I can get other people to do my homework for me, why
should I bother? ;-)

Too true.

The TIPs were pretty popular too and would doubtless have filled the bill for
the OP if he wanted a TO-220 device.


Graham

 

[Rich Grise]

On Fri, 25 Mar 2005 17:08:04 -0800, Winfield Hill wrote:

Rich Grise wrote...

Oops. Guess I missed that part. MJ2955 then. (or is that MJE?)

Depends if you want the metal TO-3 or the plastic version. But there
are much better choices than those old poor-performance transistors.
Is that why you put up the smiley? Very well, give us an alternate.

As OP said, there are billions and billions of them.

I was going by the term "favorites", which reminded me of the days as
a Radio Shack repair technician: The shop's entire budget was covered by
warranty repairs, mostly high-end stereos with blown output trannies, and
quasi-comp-sym was so common, that on my first one of these, the boss
said, "Just use 3055's." So 2N3055 was our first choice for replacement
output trannies.

<brag>
When I started there, they had about a 3-month backlog, and kept telling
customers, "It's waiting for parts". There were two other techs plus me,
and the boss, who worked occasionally. I practically single-handedly
cleaned up the backlog in about three weeks.
</brag>

I know there are sh!t-hot complementary trannies now, but as for
recommendations, all I can say is, start from the spec, and pick
and choose based on ranges of parameters to narrow down the range
of choices, and then go by price and availability.

But heck, if I can get other people to do my homework for me, why
should I bother? ;-)

Cheers!
Rich