[Amps] Changing class of operation with BIAS

[Joe Subich, W4TV]

> Question: How can you change the class of operation and conduction 
 > angle with no change to bias.

Because bias is not the only factor in class of operation/conduction
conduction angle.  Study the constant current curves for tubes (Google
tube constant current curves) ... there are several good references
like Chapter 3 of "Care and Feeding of Power Grid Tubes" and the Eimac
Tube Performance Computer.

73,

    ... Joe, W4TV


On 2019-10-31 8:34 PM, mark bitterlich wrote:
> So you are not changing the bias, even though resting current has changed, but you are changing the conduction angle and thus the class of operation (triode). Question: How can you change the class of operation and conduction angle with no change to bias. I appologize, but I am confused.
> -------- Original message --------From: "Joe Subich, W4TV" <lists at subich.com> Date: 10/31/19  19:54  (GMT-05:00) To: amps at contesting.com Subject: Re: [Amps] Changing class of operation with BIAS > If you increase plate voltage alone, which results in a higher plate > current with no signal applied, are you indeed changing the bias? Yes> or no.No.  You are changing the operating point (operating conditions) butnot the bias (unless the bias is generated by a voltage drop acrossa cathode resistor).In general, in a triode increasing late voltage will increase theidle current, increase the conduction angle of the tube and move the operating point more toward class A (class being defined by conductionangle).On the other hand, in a triode, increasing the grid bias will decreasethe idle current, decrease the conduction angle and move the operatingpoint closer to cut-off (class B or class C).73,    ... Joe, W4TVOn 2019-10-31 6:54 PM, Mark Bitterlich wrote:> It seems that my original question generated some interest, and I have> received several private replies.  A majority of them espouse some> interesting viewpoints that make me question what I thought I knew.> > So I am asking this amplifier theory question again.> > BIAS is defined as the difference in potential between the cathode and the> control grid.> > In a zero signal condition, BIAS current is a result of the difference> described above.> > Thus BIAS can be described by the difference in voltage between control grid> and cathode or as an indication of plate current with no signal applied.> > Question:> > If you increase plate voltage alone, which results in a higher plate current> with no signal applied, are you indeed changing the bias?  Yes or no.> > Thanks,> > Mark>   > _______________________________________________Amps mailing listAmps at contesting.comhttp://lists.contesting.com/mailman/listinfo/amps
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