On A Hippie Trail, Head Full Of Zombie

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#482
Luke said:
The IXTH52P10P is pretty good out to 20K at 22V, but they seem a little expensive. Do you know how it looks at 250mA?
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Bias won't affect bandwidth (while operating within it's Class A envelope) just Vds affects bandwidth.

Bias just affects transconductance.

Not sure whether you want to know transconductance at 250mA or bandwidth at 250mA

Of course this is in the context of zero feedback.
 
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#484
2 picoDumbs said:
Hockey puck results might interest some people.


At some point I might create a new thread and summarise all of this, but I wanted to be happy with my test setup/methodology etc first.
Discovering I had some crap test leads earlier has probably affected the earlier results, the comparative ranking will obviously be the same etc so qualitatively still meaningful, but I will go back and retest everything.
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Great, all the data in one thread. Btw, what is the generator output impedance ?
 
#486
Luke said:
Sorry I wasnt clear. Ideally the transconductance is flat in the audio band, out to 20khz right? The bias current influences transconductance doesnt it?
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Bias will influence transconductance but not bandwidth when operated without feedback.
That is, I wouldn't expect to see differences in bandwidth changing the bias, in my current test setup. I will try it out of curiosity though just to see.
Increasing Vds generally improves bandwidth, as seen in the results.

Of course if it were used common source and you apply feedback, at that point transconductance will most certainly improve bandwidth, so both need to be considered depending on the application.

Edit: I will do transconductance vs bias later.
 
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#487
Harris IRFP9140

Harris looks bloody interesting.
Transconductance virtually remains unchanged even with lower values of Vds.
 

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#495
bogdan_borko said:
Great, all the data in one thread. Btw, what is the generator output impedance ?
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2 picoDumbs said:
The published output impedance of the generator is 50 Ohms.
There is an additional 10 Ohms at the gate just to keep the mosfets stable.

I will be buying a new generator in the near future. The one I have is just a cheap one.
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I went back and checked the resistance at the gate, it was bloody 100 Ohms not 10 Ohms.

So 150 Ohms total assuming the function generator published data of 50 Ohms is accurate.

The new generator arrived so I will be running them again on my new toy.
 
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