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|18th November 2007, 08:19 PM||#1|
Join Date: Jan 2007
Location: Jerusalem, Israel
Datasheets: RC coupled amp VS. typical characteristics
A couple of times I've seen datasheets where cathode resistor in "typical operations" was significantly smaller than in "RC coupled amp table". I understand you can bias it any way you like but still cannot understand what's the story.
5670 - double triode.
see page 3: cass A1 amplifier, cathode resistor = 240 ohm.
in class A RC coupled amplifier table below the lowest cathode resistor is 900 ohm.
5719 - submin triode
page 1: characteristicsn- plate 100V, cathode resistor = 1.5K.
page 6: RC coupled amp - plate 100V, cathode res. = 2.7K and higher.
5718 - submin triode
characteristics: cathode 150 ohm - plate 100V
RC amp - cathode 1K and higher (under 100V)
I'm sure I am missing some point. Why is that difference?
|18th November 2007, 09:46 PM||#2|
Join Date: May 2005
Blog Entries: 7
Re: Datasheets: RC coupled amp VS. typical characteristics
Lots of VT specs also suggest typical circuits. I ignore these completely, and design based on loadlines. Most of those sample circuits are based on 5.0% THD, which is pretty awful. Nor is it always possible to use the specified Vpp. I can do better by picking my own Q-points and distortion figures from the plate characteristics. Consider it to be nothing more than a cheat for lazy designers.
There are no foxes in atheistholes
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