Sub for BC549C

This transistor has a high beta. Trying to build a mic amp and several designs use this transistor. Thanks Mike

I read in sci.electronics.design that amdx wrote (in ) about 'Sub for BC549C', on Tue, 18 Jan 2005:

If this is for your stethoscope project, the beta is probably not very critical. But you don't even say which country you are in, so how can anyone suggest a substitute that you will be able to get?

Where did you find the design with the BC549C? If it's on the web, a URL would be helpful. Otherwise, can you put the circuit diagram on a web page? Or on a.b.s.e?

Totally normal for a modern silicon device.

Indeed they do these days..

Before the BC549, the BC184(C) would have been typical.

What's your problem with the BC549 ? It's in full production from multiple suppliers. You may not actually need the C grade - but I guess from your question that your experience isn't sufficient to work that out. The C grade is often used by companies standardising on parts. I actually normally use the B grade.

Graham

Watch out for the reversed BCE connections.

NF is also specified @ 10k ohms for the 2N5089 but 2k ohms for the BC549. Suggesting a lower noise voltage for the BC549 - although this may or may not be important depending on the placement of this part in the overall circuit. Neither part is really suitable for genuine low noise amplificiation of typical low-Z mics as a first stage device. You'll need a pnp part for that with low intrinsic resistance such as the 2SA1084.

Graham

Yes it is for the stethoscope project, I'm in the USA and I don't know how anyone could suggest a substitute that I would be able to get. ( I feel properly spanked)

I have built this with a 2N2222 and it works fine except the gain is to low. So I added a second stage consisting of the following circuit ,

This not the way to go, the signal is distorted on the top of the waveform.

I'm thinking of putting two of the first stage in series and see if the distortion is better. Any thoughts?

Thanks for your help Mike

I read in sci.electronics.design that amdx wrote (in ) about 'Sub for BC549C', on Wed, 19 Jan 2005:

This doesn't requires a BC549C! It is also a bit TOO simple for optimum performance.

This is not a very good design.

Not the most promising idea. Unfortunately, I don't have time at this instant to design something for you: I have to leave for a meeting in London shortly. Maybe tomorrow.

Which do you mean? The circuit you link

BC547B

------ European equivalent: BC337 USA: 2N5818 Old Radio Shack: 276-2009

BC549C

------ European equivalent: BC548C-->BC547C-->BC239 USA: 2N5818 Old Radio Shack: 276-2009

But both could be replaced by *hundreds* of other possibles of similar spec. Here's the data for the BC547B:

Package Vcb(max) Vce(max) Veb(max) Ic(max) Tj(max) Ptot TO92 50V 45V 6V 100mA 150C 500mW Ft(min) Cob(max) Hfe(min) HfeBias