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Old 22nd November 2012, 12:18 PM   #681
44250 is offline 44250  Serbia
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Quote:
Originally Posted by AndrewT View Post
No,
I get accused of being unhelpful.
well,do you?
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Old 22nd November 2012, 12:22 PM   #682
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thank u for the reply andrew and 44250.
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Old 22nd November 2012, 12:43 PM   #683
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hi apex sir ,
like this when i measured the emitor resistor voltage, any solution?
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Old 22nd November 2012, 01:39 PM   #684
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Originally Posted by nazirdigi View Post
thank u for the reply andrew and 44250.
don't mention it...
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Old 22nd November 2012, 01:43 PM   #685
AndrewT is offline AndrewT  Scotland
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Quote:
Originally Posted by nazirdigi View Post
................i measured the emitor resistor voltage, any solution?
the irf240 does not have an emitter.
Quote:
For mosFET output stage it's variation in Vgs that leads to even bigger variations in Id and that shows when reading individual Vrs (voltage across the source resistor).
solution:- Take out all your FETs and select for equal Vgs at the operating current.
Quote:
and that variation in Vgs for paralleled mosFETs is why it is absolutely important that devices be selected for very close Vgs at the target operating current for the amplifier output stage.
Am I wasting my time with unhelpful posts?
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regards Andrew T.
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Old 22nd November 2012, 01:59 PM   #686
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MOSFET Matching
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Old 22nd November 2012, 03:03 PM   #687
44250 is offline 44250  Serbia
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Unhappy bad luck

Quote:
Originally Posted by AndrewT View Post
the irf240 does not have an emitter.
solution:- Take out all your FETs and select for equal Vgs at the operating current.Am I wasting my time with unhelpful posts?
that is why i said:

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Originally Posted by 44250 View Post
don't mention it...
after his:

Quote:
Originally Posted by nazirdigi View Post
hi apex sir ,
like this when i measured the emitor resistor voltage, any solution?
he did not take us seariously;me mistaking and you correcting...
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Old 22nd November 2012, 03:57 PM   #688
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apex , andrew, 44250 thanks for the help and coperation.
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Old 22nd November 2012, 04:29 PM   #689
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don't mention it...
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Old 10th December 2012, 02:00 PM   #690
Shelah is offline Shelah  Zambia
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guys i still have a problem with the 30mA bias current issue. in terms of voltage accross the source resistors (0.47ohms), is the voltage acccros them 14.1mV?
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