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Chip Amps Amplifiers based on integrated circuits

Chip amp decoupling/snubberizing caps
Chip amp decoupling/snubberizing caps
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Old 7th December 2017, 09:24 PM   #11
DF96 is offline DF96  England
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If you omit the 0.1uF bypass caps in the PSU then you might not need the PSU snubber. The electrolytic ESR will dampen any resonance created by the local chip decouplers. As others have said, any film cap will do.
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Old 7th December 2017, 10:30 PM   #12
00940 is offline 00940  Belgium
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Make Cs 4.7uF/100V X7R. Such caps were not easily available when the datasheet was written but since they are now we might as well use them.

Cz can be mkt without any worries. Don't waste money on a mkp there.

Btw, your schematic is incomplete. You are missing the network in // with the feedback resistor (Cf-Rf2 in the datasheet) and one cap in between the + and - inputs (Cc). The single supply schematic is strangely more complete than the dual supply one in the datasheet.

You might also want to add an input cap (safer if you don't have an offset protection) and increase the feedback capacitor to 100uF.
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Last edited by 00940; 7th December 2017 at 10:42 PM.
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Old 7th December 2017, 11:58 PM   #13
ggidzinski is offline ggidzinski  United States
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Quote:
Originally Posted by Mark Whitney View Post
I think this is the one used by chipamp.
BFC241641004 Vishay / BC Components | Mouser Europe
Thanks. That's the closest offering from BC to the original blue box caps but they changed the width.

George
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Old 8th December 2017, 10:03 AM   #14
AndrewT is offline AndrewT  Scotland
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The 1r0 snubbers are in the wrong place on the output of the PSU.
They should be across the transformer secondaries.
DF said
Quote:
If you omit the 0.1uF bypass caps in the PSU then you might not need the PSU snubber.
remove the 0.1uF, it can only increase the risk of ringing.
DC block on the input missing. (22k suits either 4u7F BiPolar, or two 10uF back to back)
RF attenuation on the input missing. (1k0 suits 330pF to 1nF across the 22k)
DC block on the NFB lower leg far too small. (680r suits 220uF, or 330uF)
00940 said
Quote:
You are missing the network in // with the feedback resistor (Cf-Rf2 in the datasheet) and one cap in between the + and - inputs (Cc). The single supply schematic is strangely more complete than the dual supply one in the datasheet.
read the datasheets again and ask if you don't understand.
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Last edited by AndrewT; 8th December 2017 at 10:12 AM.
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Old 8th December 2017, 10:04 AM   #15
scottjoplin is offline scottjoplin  Wales
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Snubbers are placed across switching elements, often across rectifiers, I presume they were adopted by the gainclone community due to the minimal smoothing used in the design and their small size?
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Old 8th December 2017, 10:22 AM   #16
AndrewT is offline AndrewT  Scotland
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Quote:
Originally Posted by scottjoplin View Post
Snubbers are placed across switching elements, often across rectifiers
Yes, across the ~~ terminals since this is effectively across the secondary.
Quote:
, I presume they were adopted by the gainclone community due to the minimal smoothing used in the design and their small size?
because he did not know what the effect of adding the low esr cap to the inductance in the nearby circuit when a step change in current was imposed.
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Old 8th December 2017, 11:23 AM   #17
DF96 is offline DF96  England
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There is a certain school of 'design' which always adds a 'bypass' across every big cap, and scatters 'snubbers' liberally around (yet sometimes avoiding the places where a snubber might do some good). In some cases, the otherwise unnecessary snubbers deal with the harm created by the unnecessary bypasses.
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Old 8th December 2017, 05:46 PM   #18
ggidzinski is offline ggidzinski  United States
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I may need to rethink my approach. I chose the Chip Amp.com boards as my starting/learning point for my first gain clone build. The schematics I provided are those boards and BOM. After reAding these comments it appeRs that this design is not held in high regard, although I am learning a lot. I have a few other boards, maybe I'll post the schematics and see if any of those get better reviews.

George
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Old 8th December 2017, 06:13 PM   #19
AndrewT is offline AndrewT  Scotland
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it is often possible to add components or change components to a pre-made PCB.
Have a good look at your PCB and see what mods/additions are feasible. This is a really good learning experience in becoming familiar with the PCB, it's layout, what each component does and what is possible to change in someone else's design.

Only where all your desired and some of the NEEDED mods are impractical do you throw the PCB away.
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