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Old 22nd December 2003, 01:09 PM   #161
JDeV is offline JDeV  South Africa
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Join Date: Oct 2002
Location: Cape Town
Quote:
Originally posted by Optical
What is that IC (opamp?) for?
is it a differential driver?
The OpAmp is a voltage follower input buffer to provide a higher input impedance, ... if I understand correct.


Quote:
The input impedance of the inverting amplifier is essentially
resistor, Ri. The value of this resistance affects the
gain setting of the amplifier as well as the low frequency
rolloff in conjunction with Ci. There is a tradeoff between
having a low frequency rolloff, a high input impedance
and a small capacitor size and value. It is critical to have
a flat band response down to 20Hz while it is equally
important to have a high enough input impedance so that
heavy loading does not occur from the preamp stage.
Using large valued low-cost capacitors implies the use of
leaky electrolytics which affect the output offset voltage.
Electrolytic capacitors are also less linear than other
premium caps and should not be used in the signal path
when not necessary. This tradeoff issue is the toughest
portion of the design. The amplifier gain setting is just as
one would expect for an inverting op amp. Of course, the
input impedance issue can be quickly resolved by using a
voltage follower as an input buffer, ....
.... as described in this application note from National.

http://www.national.com/an/AN/AN-1192.pdf

200W Bridged/parallel circuit:
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Old 20th March 2005, 07:22 AM   #162
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Join Date: Mar 2005
Location: Toronto
Default Heavy PSU

Quote:
Originally posted by SkinnyBoy
what about this? lol

Found this circuit in a engineering manual from an
audio equip. manufacturer


don't know if this will work with your heavy draw
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Old 23rd March 2005, 08:14 PM   #163
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Join Date: Mar 2005
Location: Toronto
Default Re: Heavy PSU

Quote:
Originally posted by biodrone



Found this circuit in a engineering manual from an
audio equip. manufacturer


don't know if this will work with your heavy draw

I believe the part that looks like a capacitor is actually a MOV
(Metal Oxide Varistor)

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