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Folded/shunt cascode differential question
Folded/shunt cascode differential question
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Old 14th March 2018, 10:33 AM   #41
Rod Coleman is offline Rod Coleman  United Kingdom
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Folded/shunt cascode differential question
R-anode looks too small. 3W wirewound recommended.
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Old 14th March 2018, 12:36 PM   #42
mogliaa is offline mogliaa  United Kingdom
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Folded/shunt cascode differential question
You need a protection zener for the lower device if J112. A 15v one should work well

The IXTP08n100d as well as the other higher current versions from IXYS have a higher VGS value for lower current (<50mA) which will allow the J112 to operate at higher VDS so capacitances at play are reduced. Overall FR of the stage is improved at HF this way.
Btw: and they sound better!
Ale
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Old 14th March 2018, 05:38 PM   #43
john_tracy is offline john_tracy  United States
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From experience I'd use an IXYS 8N50D on the bottom of the anode cascode.
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Old 15th March 2018, 02:36 AM   #44
Sodacose is offline Sodacose  United States
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Epic tip on the ammo pack layout! Will also add zener for the JFET, up the anode resistor dissipation and make the anode load a cascode rather than a single depletion fet.
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Old 15th March 2018, 03:01 PM   #45
Sodacose is offline Sodacose  United States
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Updates! Board grew a bit, but I was able to route everything much more cleanly thanks to the ammo pack suggestion and (ironically) adding a few more/bigger parts. Now about 3.75" by 2.25" and accommodates a standard 1" spaced heatsink for the higher dissipation TO220.

Click the image to open in full size.

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Gotta say, laying out boards is kind of fun (in the way that ptp wire routing OCD is fun).
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Old 15th March 2018, 03:24 PM   #46
Ketje is offline Ketje  Belgium
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Can't help it, does remind me of this
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