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Old 9th October 2017, 07:58 AM   #1131
2 picoDumbs is offline 2 picoDumbs  Australia
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Output stage or front end preamp circuit?
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Old 9th October 2017, 09:21 AM   #1132
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I meant on photo = what's missing .....
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Old 9th October 2017, 09:25 AM   #1133
Ian Macmillan is offline Ian Macmillan
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Quote:
Originally Posted by 2 picoDumbs View Post
No need for bias stabilisation.
Just catching up with the latest on this thread...

OK, so no need for bias stabilization from a thermal perspective but what about current sharing between the devices? Is matching the devices sufficient to avoid any current hogging?
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Old 9th October 2017, 10:21 AM   #1134
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Quote:
Originally Posted by Zen Mod View Post
I meant on photo = what's missing .....

Ok.
If people want to try it out it's important to have big heatsinks, use keratherm etc to minimise delta T between turn on and at full operating conditions.
Not absolutely mandatory but it will significantly improve the delta bias current between start up and operating conditions.

Obviously matching is important, the devices are matched to within 3% of each other I can explain how I did this. That is the current through each device is not more than 3% different from each other at the bias point.
Not too difficult.
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Last edited by 2 picoDumbs; 9th October 2017 at 10:25 AM.
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Old 9th October 2017, 11:42 AM   #1135
2 picoDumbs is offline 2 picoDumbs  Australia
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Quote:
Originally Posted by Ian Macmillan View Post
what about current sharing between the devices? Is matching the devices sufficient to avoid any current hogging?
Yes matching is sufficient but I think I would need to explain my procedure, of how I do it.
In my circuit current through each mosfet does not differ by more than 3%.
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Old 9th October 2017, 01:57 PM   #1136
Ian Macmillan is offline Ian Macmillan
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That is pretty impressive. I had thought one of the reasons why the hockey puck solution was favoured is due to the need for only one (per rail) and hence no current hogging issues without degeneration.
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Old 9th October 2017, 02:59 PM   #1137
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you got it right regarding pucks

they're convenient from several reasons
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Old 9th October 2017, 07:50 PM   #1138
2 picoDumbs is offline 2 picoDumbs  Australia
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Hockey pucks are for sissies.
Hahaha
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Old 9th October 2017, 08:08 PM   #1139
needtubes is offline needtubes  United States
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Quote:
Originally Posted by 2 picoDumbs View Post
Hockey pucks are for sissies.
Hahaha
Implying real men match MOSFETs?
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Old 9th October 2017, 08:12 PM   #1140
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yup

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