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Micro-power audio amplifier

Started by ozzy October 11, 2011
Hi,

I want to have a go at building the amplifier shown on page 952 (fig
14.29) of AofE (2nd ed).  However I can't get a hold of the
transistors used:  (NPN) MPS6547 and (PNP) 2N4957.  Does anyone know
where those parts can be obtained from, or if any direct replacements
were ever made?


Cheers,

Osman.
The AofE section 14.11 explains how the transistor was chosen;
you can peruse the vendors' listings of RF small signal NPN and
PNP transistors to find those with similar characteristics.
The 2N4957, for instance, seems to have been chosen for
its Ccb of 0.6 pF at 2V; start looking at PNP datasheets
for a Cc versus Vc plot.   BFT93 is a tad high, at 1.2 pF,
but BFT92 is about right.
On Oct 12, 2:43=A0am, whit3rd <whit...@gmail.com> wrote:
> The AofE section 14.11 explains how the transistor was chosen; > you can peruse the vendors' listings of RF small signal NPN and > PNP transistors to find those with similar characteristics. > The 2N4957, for instance, seems to have been chosen for > its Ccb of 0.6 pF at 2V; start looking at PNP datasheets > for a Cc versus Vc plot. =A0 BFT93 is a tad high, at 1.2 pF, > but BFT92 is about right.
Watch out. The BFT92 and 93 parts are broad-band transistors with a gain bandwidth of about 5GHz which will oscillate at a few GHz without a "base-stopper" - roughly 22R of resistance close to - and in series with - the base lead. Their base-emitter breakdown voltage is also unusually low, at around 2V. The 2N4957 is clearly of a similar nature - 1.6GHz and a 3V base- emitter breakdown voltage http://www.semicoa.com/wp-content/uploads/2N4957.pdf if somewhat slower and more conventionally packaged. -- Bill Sloman, Nijmegen http://www.dz863.com/downloadpdf-vdmpxgcfcfbs-2N4957.pdf
On Oct 11, 6:34=A0pm, ozzy <osma...@gmail.com> wrote:
> Hi, > > I want to have a go at building the amplifier shown on page 952 (fig > 14.29) of AofE (2nd ed). =A0However I can't get a hold of the > transistors used: =A0(NPN) MPS6547 and (PNP) 2N4957. =A0Does anyone know > where those parts can be obtained from, or if any direct replacements > were ever made? > > Cheers, > > Osman.
There are some MPS6547's http://www.findchips.com/avail?part=3Dmps6547 also the 2n4957's, but they aren't giving them away.... http://www.findchips.com/avail?part=3D2n4957 (Wish I had a few I could sell you for ~$100 each :^) George H. Hey maybe Win Hill will have some suggestions in the 'long awaited' third edition.
On Wed, 12 Oct 2011 08:42:46 -0700 (PDT), George Herold
<gherold@teachspin.com> wrote:

>On Oct 11, 6:34&#2013266080;pm, ozzy <osma...@gmail.com> wrote: >> Hi, >> >> I want to have a go at building the amplifier shown on page 952 (fig >> 14.29) of AofE (2nd ed). &#2013266080;However I can't get a hold of the >> transistors used: &#2013266080;(NPN) MPS6547 and (PNP) 2N4957. &#2013266080;Does anyone know >> where those parts can be obtained from, or if any direct replacements >> were ever made? >> >> Cheers, >> >> Osman. > >There are some MPS6547's > >http://www.findchips.com/avail?part=mps6547 > >also the 2n4957's, but they aren't giving them away.... >http://www.findchips.com/avail?part=2n4957 > >(Wish I had a few I could sell you for ~$100 each :^) > >George H. > >Hey maybe Win Hill will have some suggestions in the 'long awaited' >third edition.
Or stop, and think, and analyze. Then substitute readily available devices ?:-) This is supposed to be a DESIGN group, but you'd never know it :-( ...Jim Thompson -- | James E.Thompson, CTO | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona 85048 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | I love to cook with wine. Sometimes I even put it in the food.
On 10/11/2011 5:34 PM, ozzy wrote:
> Hi, > > I want to have a go at building the amplifier shown on page 952 (fig > 14.29) of AofE (2nd ed). However I can't get a hold of the > transistors used: (NPN) MPS6547 and (PNP) 2N4957. Does anyone know > where those parts can be obtained from, or if any direct replacements > were ever made? > > > Cheers, > > Osman.
I was interested in that circuit, too. Although I have not yet built it, I selected the MPSH10 NPN and the MPSH81 PNP to try in it. Good luck, John S
On Oct 12, 12:00=A0pm, Jim Thompson <To-Email-Use-The-Envelope-I...@On-
My-Web-Site.com> wrote:
> On Wed, 12 Oct 2011 08:42:46 -0700 (PDT), George Herold > > > > > > <gher...@teachspin.com> wrote: > >On Oct 11, 6:34=A0pm, ozzy <osma...@gmail.com> wrote: > >> Hi, > > >> I want to have a go at building the amplifier shown on page 952 (fig > >> 14.29) of AofE (2nd ed). =A0However I can't get a hold of the > >> transistors used: =A0(NPN) MPS6547 and (PNP) 2N4957. =A0Does anyone kn=
ow
> >> where those parts can be obtained from, or if any direct replacements > >> were ever made? > > >> Cheers, > > >> Osman. > > >There are some MPS6547's > > >http://www.findchips.com/avail?part=3Dmps6547 > > >also the 2n4957's, but they aren't giving them away.... > >http://www.findchips.com/avail?part=3D2n4957 > > >(Wish I had a few I could sell you for ~$100 each =A0:^) > > >George H. > > >Hey maybe Win Hill will have some suggestions in the 'long awaited' > >third edition. > > Or stop, and think, and analyze. =A0Then substitute readily available > devices ?:-) > > This is supposed to be a DESIGN group, but you'd never know it :-(
Yeah, and some of us are still in the 'cut and paste' stage. I thought the OP might not know about findchips website. George H.
> > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =
=A0 =A0 ...Jim Thompson
> -- > | James E.Thompson, CTO =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =
=A0 =A0| =A0 =A0mens =A0 =A0 |
> | Analog Innovations, Inc. =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =
=A0 | =A0 =A0 et =A0 =A0 =A0|
> | Analog/Mixed-Signal ASIC's and Discrete Systems =A0| =A0 =A0manus =A0 =
=A0|
> | Phoenix, Arizona =A085048 =A0 =A0Skype: Contacts Only =A0| =A0 =A0 =A0 =
=A0 =A0 =A0 |
> | Voice:(480)460-2350 =A0Fax: Available upon request | =A0Brass Rat =A0| > | E-mail Icon athttp://www.analog-innovations.com| =A0 =A01962 =A0 =A0 | > > I love to cook with wine. =A0 =A0 Sometimes I even put it in the food.- H=
ide quoted text -
> > - Show quoted text -
On Wed, 12 Oct 2011 11:23:48 -0700 (PDT), George Herold
<gherold@teachspin.com> wrote:

>On Oct 12, 12:00&#2013266080;pm, Jim Thompson <To-Email-Use-The-Envelope-I...@On- >My-Web-Site.com> wrote: >> On Wed, 12 Oct 2011 08:42:46 -0700 (PDT), George Herold >> >> >> >> >> >> <gher...@teachspin.com> wrote: >> >On Oct 11, 6:34&#2013266080;pm, ozzy <osma...@gmail.com> wrote: >> >> Hi, >> >> >> I want to have a go at building the amplifier shown on page 952 (fig >> >> 14.29) of AofE (2nd ed). &#2013266080;However I can't get a hold of the >> >> transistors used: &#2013266080;(NPN) MPS6547 and (PNP) 2N4957. &#2013266080;Does anyone know >> >> where those parts can be obtained from, or if any direct replacements >> >> were ever made? >> >> >> Cheers, >> >> >> Osman. >> >> >There are some MPS6547's >> >> >http://www.findchips.com/avail?part=mps6547 >> >> >also the 2n4957's, but they aren't giving them away.... >> >http://www.findchips.com/avail?part=2n4957 >> >> >(Wish I had a few I could sell you for ~$100 each &#2013266080;:^) >> >> >George H. >> >> >Hey maybe Win Hill will have some suggestions in the 'long awaited' >> >third edition. >> >> Or stop, and think, and analyze. &#2013266080;Then substitute readily available >> devices ?:-) >> >> This is supposed to be a DESIGN group, but you'd never know it :-( > >Yeah, and some of us are still in the 'cut and paste' stage. > >I thought the OP might not know about findchips website. > >George H. >>
[snip] I have no problem with the findchips reference, but I'd be thrilled if someone (besides me :-) could actually analyze the circuit. ...Jim Thompson -- | James E.Thompson, CTO | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona 85048 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | I love to cook with wine. Sometimes I even put it in the food.