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Old 13th January 2005, 03:01 AM   #1
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Default Bias filtering

I'm putting together a three pin regulated variable bias supply.

Should I get a fitting, hmmm free, result using the 10,000uF per amp rule for capacitance?

Or should I try something higher?
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Old 13th January 2005, 05:40 AM   #2
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Er...

*choke*

Just how much current you intending on drawing from this ******* bias supply anyways?!

Oh... per amp... still 5x too much! ;O)

Besides, bias is applied through a grid leak, the other end of which is almost always connected to a low impedance triode. In fact, you can run through the voltage dividers thus represented and find exactly how much ripple actually appears _at the grid_. Then for extra points, determine the CMRR of the PP output stage! (If...that happens to be what you are biasing..)

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Old 13th January 2005, 12:43 PM   #3
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Quote:
Er...

*choke*

Just how much current you intending on drawing from this ******* bias supply anyways?!
You mean you DON'T weld with your bias supply?!

Quote:
Oh... per amp... still 5x too much! ;O)
Apparently, if I use tantalum, 125x too much!

Quote:
Besides, bias is applied through a grid leak, the other end of which is almost always connected to a low impedance triode. In fact, you can run through the voltage dividers thus represented and find exactly how much ripple actually appears _at the grid_.
I think I see what you're saying, but... since the grid can't emit electrons, theoretically anyway..., whilst it's biased negatively it should have a very high resistance between it and the cathode shouldn't it?

"The grid of a tube normally presents a very high impedance load to the driving source when it is biased in the negative region." Aiken of Aiken Amps.
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Old 13th January 2005, 04:50 PM   #4
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AC. AC impedance. Backwards, behind the coupling cap, you know...

Otherwise yes, the grid has a high DC impedance - until you overdrive it and it becomes a diode part of the cycle. Hehe..

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