Question About Transistor Matching

[SSDIY]

Hi I am new to this forum. I got the following transistor matching circuit from the internet it is quite simple and easy to build but the upper section (for NPN measurement) of the circuit has one 10K resistor connected between the two transistors while the lower section (for PNP measurement) has none. Would anyone please tell me is this a drawing mistake? Which one is correct? Thanks.

 

[fritz39]

Your picture is too small to see.

 

[SSDIY]

Try again

 

[planet10]

That is still the same size as the last posted image.

dave

 

[sandyK]

Image size

Planet10
I now have the same problem when posting images here, that are hosted by ImageShack. Even though the original picture may be quite large, since the DIYAudio upgrade, it is the thumbmail that is being used , instead of being able to use the clickable option for a large image. Perhaps as a Moderator, you may be able to find out why the original option no longer works.
It certainly still functions in other forums.
Regards
SandyK

 

[SSDIY]

The original image is a Jpeg 100k file. It has been compressed when uploading to the thread. Could anyone help to post it with a bigger size if I send him the file?

 

[Jan Dupont]

Make a PDF file and attach that or email it to me..... 😉

 

[SSDIY]

Make a PDF file and attach that or email it to me..... 😉

Hi Jan

Thank you for your help. I am pleased to attach a pdf file of the circuit.

Thanks
Albert

 

[peranders]

First of all, why do you want to match transistors? The question is for leading you to something else. Maybe you don't need to match at all?

 

[jackinnj]

First of all, why do you want to match transistors? The question is for leading you to something else. Maybe you don't need to match at all?

Perhaps he's using them for a current source -- nice to have them matched.

 

[Jan Dupont]

Ssdiy 😉

 

[peranders]

Perhaps he's using them for a current source -- nice to have them matched.

Sometimes it's better to match them in the actual circuit.

 

[SSDIY]

First of all, why do you want to match transistors? The question is for leading you to something else. Maybe you don't need to match at all?

Hi peranders
As far as I know matching differential transistors will minimize offset voltage and matching output transistors will help to get better reliability of the amp.

 

[SSDIY]

Perhaps he's using them for a current source -- nice to have them matched.

Hi Jack

This is one of the goals of matching.

 

[SSDIY]

Ssdiy 😉

Hi Jan

Any comment for the circuit?

 

[Jan Dupont]

Hi Jan

Any comment for the circuit?

Back to your initial question; I think the 10K is missing in the PNP measurement circuit..... ?

Also if you do want to match transistors, I miss the possibility to match them at different currents like 100uA, 1mA and 10mA....

As to peranders suggestion about matching them in the actual circuit, I agree that that is the most correct way of doing it. Build a copy of the circuit (e.g. current source), and match the trannies at e.g. 3mA

 

[pooge]

You can try another matching circuit:
http://www.diyaudio.com/forums/solid-state/146693-john-curls-blowtorch-preamplifier-part-ii-19.html#post1901774

 

[SSDIY]

Sometimes it's better to match them in the actual circuit.

Hi peranders & Jan

This is a good idea I also think it is better to match the transistors in the actual circuit but would you please give more information about how to perform the measurement to match transistors. Thanks

 

[SSDIY]

You can try another matching circuit:
http://www.diyaudio.com/forums/solid-state/146693-john-curls-blowtorch-preamplifier-part-ii-19.html#post1901774

Hi pooge

Thank you for the advice of the matching circuit. I will take some time to study it.

 

[SSDIY]

Would anyone please tell what is the difference between the following matches:

For Fets: idss & Vgs

For BJTs: hFE & Vbe

Thanks