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I'm trying to allow my amplifier output stage to have variable operating points without the need to manually change resistors.
I think I've got it figured out for the input stage but the output stage is another matter.
For a WCF I'm thinking of putting a CCS on the cathode and a CVS on the anode, the CCS setting the current and the CVS setting the voltage. Unfortunately it's not working out the way I'd hoped.
The far left is the original circuit, the middle is the CCS on cathode and the far right is the CVS. Everything is dandy until I change the amplitude of the signal then everything gets thrown off.
What am I missing? Why does a change in AC amplitude screw over the operating points?
Follow Ups:
Far too complicated , looks like it is intended for headphones so there will be offset until warmup and even then drift which will probably be not too healthy . Should really be a coupling cap to the load which is maybe what is throwing off your simulation
Al
It's very difficult to see the schematic on my screen. That aside, why are you using active devices to represent the voltage source? Doesn't the B+ supply (battery) provide a sufficiently low impedance?
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Buy Chinese. Bury freedom.
Why does a change in AC amplitude screw over the operating points?
You need to plot a load line and choose the right DC operating points around the center of that load line.Once you choose the correct operating points,it should be stable regardless of signal.It's messing with the operating points because it's not running at the correct points for your tubes and design..Maybe someone else can chime in on that does this a lot.
Nobody ever went broke underestimating the intelligence of the American public
H. L. Mencken
I did choose the center of the load line. But If I change the AC amplitude from 1v to 10v or something then all of the operating points get thrown off for some reason,
Coin
I have found that using a spice program coordinates can be totally different from the actual build.When you say the operating points change,how are you verifying this? Are you using a program or actual measurement of the physical build at this point? Spice programs can be very deceiving.
Nobody ever went broke underestimating the intelligence of the American public
H. L. Mencken
Edits: 02/06/16
Anode or cathode?
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