ALEPH-X bias reisistor 221R matching

fjc · 27th November 2004, 04:55 PM

Working on a ALEPH-X project, a version originated from
Grey, has three MOS power instead one on each side, top
and botom. Grey kindly reminded the importance of the match, bottom half, and nicer for the top pairs too.

If the circuit (one channel) is divided into four areas:top left; right, botom left;right.
The best I can get from the 1% 0.5W dale R60C/D is listed ascendingly from R1 to R12 (see botom).

I am thinking group R4 to R9 to the botom, R4,5,6 assigned to the (3 parallel bias resistors) botom left ,
R7,8,9 to the botom right.
Then, choose R1,2,3 for the top left, R10,11,12 for the top right.
My reasoning: closer match for the botom L & R, closer match for the top and botom.

Is this arrangement proper?
I use the same approach for the output resistors ( o.47 ohm, 3-5W).

R1 220.48
R2 220.49
R3 220.49
R4 220.53
R5 220.55
R6 220.56
R7 220.61
R8 220.68
R9 220.68
R10 220.70
R11 220.70
R12 220.75

fjc

Netlist · 27th November 2004, 05:24 PM

Quote:

Originally posted by fjc
Is this arrangement proper?

Yes, assuming you mean 0.220 ohm instead of 220 ohm.

/Hugo

uli · 27th November 2004, 05:55 PM

the exact value!

In real life its not possible to get a perfect match, as every mosfet is unique in his behaviour. taking any 1% resistor will work fine.

Uli

UrSv · 27th November 2004, 06:23 PM

Seems you are talking about the resistors on the gates of the FETs. IMHO, they don't need any matching at all.

wuffwaff · 28th November 2004, 08:43 AM

as long as you are using 1% resistors you don´t have to match them. It is only of some importance when using 5% or 10% resistors like the MCP71.
It is of more importance that the fets where the sence resistor is connected are really well matched.

William

fjc · 28th November 2004, 07:22 PM

"It is of more importance that the fets where the sence resistor is connected are really well matched"

Please advise the location of the sense resistors. In Grey's diagram for example, thanks.

FET has been measured and match with the Vgs.

thank you, everyone,

fjc

fjc · 4th December 2004, 02:34 PM

The sensing resistor is the source/ output resistor, just fond the definition, it was matched before matching the bias R, thanks for the reminding,
cheers,
fjc

27th November 2004, 04:55 PM	#1
fjc diyAudio Member Join Date: May 2004 Location: Taiwan	ALEPH-X bias reisistor 221R matching Working on a ALEPH-X project, a version originated from Grey, has three MOS power instead one on each side, top and botom. Grey kindly reminded the importance of the match, bottom half, and nicer for the top pairs too. If the circuit (one channel) is divided into four areas:top left; right, botom left;right. The best I can get from the 1% 0.5W dale R60C/D is listed ascendingly from R1 to R12 (see botom). I am thinking group R4 to R9 to the botom, R4,5,6 assigned to the (3 parallel bias resistors) botom left , R7,8,9 to the botom right. Then, choose R1,2,3 for the top left, R10,11,12 for the top right. My reasoning: closer match for the botom L & R, closer match for the top and botom. Is this arrangement proper? I use the same approach for the output resistors ( o.47 ohm, 3-5W). R1 220.48 R2 220.49 R3 220.49 R4 220.53 R5 220.55 R6 220.56 R7 220.61 R8 220.68 R9 220.68 R10 220.70 R11 220.70 R12 220.75 fjc

27th November 2004, 05:55 PM	#3
uli diyAudio Member Join Date: Dec 2002 Location: Vienna, Austria	don´t be too fussy about the exact value! In real life its not possible to get a perfect match, as every mosfet is unique in his behaviour. taking any 1% resistor will work fine. Uli __________________ 'Jazz is not dead, it just smells funny' F.Zappa

27th November 2004, 06:23 PM	#4
UrSv diyAudio Member Join Date: Jan 2002 Location: Sweden	Seems you are talking about the resistors on the gates of the FETs. IMHO, they don't need any matching at all. __________________ UrSv Those who say it can't be done should not stop those who are doing it.

28th November 2004, 08:43 AM	#5
wuffwaff diyAudio Member Join Date: Aug 2001 Location: Ingolstadt Germany	as long as you are using 1% resistors you don´t have to match them. It is only of some importance when using 5% or 10% resistors like the MCP71. It is of more importance that the fets where the sence resistor is connected are really well matched. William __________________ een ooievaar is geen konijn want zijn oren zijn te klein!

28th November 2004, 07:22 PM	#6
fjc diyAudio Member Join Date: May 2004 Location: Taiwan	sense resistor "It is of more importance that the fets where the sence resistor is connected are really well matched" Please advise the location of the sense resistors. In Grey's diagram for example, thanks. FET has been measured and match with the Vgs. thank you, everyone, fjc


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4th December 2004, 02:34 PM	#7
fjc diyAudio Member Join Date: May 2004 Location: Taiwan	The sensing resistor is the source/ output resistor, just fond the definition, it was matched before matching the bias R, thanks for the reminding, cheers, fjc

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