The datasheets for this tube only give pentode characteristics, and none for the triode strapped configuration. Is there a way to calculate/estimate things like the mu and Rp of a triode strapped pentode from the pentode data?

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- Thread starter mnturner
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The datasheets for this tube only give pentode characteristics, and none for the triode strapped configuration. Is there a way to calculate/estimate things like the mu and Rp of a triode strapped pentode from the pentode data?

ah here on the bottom seem triode curves http://www.shinjo.info/frank/sheets/127/6/6418.pdf .

seems like a nice tube.

the screen grid voltage controls the current at a with a certain (more or less) fraction of the control grid sensitivity, in volts giving a certain change in current. the ratio is the effective mu; µg1/g2. one can roughly trace it out of the penthode curves. (since the g2does a certain magnitude of current, for the voltage it has indicated on graphs)

this tube has a quite low plate current so can only drive not too big mosfets fast enough.

the rp seems to be around 16~17k.

if one looks at a suitable point to trace out a easily countable amount, at a fixed g1 voltage (say -1 here) with 20V Uplate say 240 uA, with 30V 800uA, that is 560 uA for 10 V, 17.8K (oops i was off ;p)

the grid controls about that amount (560 uA) with about 1V variation. one may thus guess the µ is around 10.

seems like a nice tube.

the screen grid voltage controls the current at a with a certain (more or less) fraction of the control grid sensitivity, in volts giving a certain change in current. the ratio is the effective mu; µg1/g2. one can roughly trace it out of the penthode curves. (since the g2does a certain magnitude of current, for the voltage it has indicated on graphs)

this tube has a quite low plate current so can only drive not too big mosfets fast enough.

the rp seems to be around 16~17k.

if one looks at a suitable point to trace out a easily countable amount, at a fixed g1 voltage (say -1 here) with 20V Uplate say 240 uA, with 30V 800uA, that is 560 uA for 10 V, 17.8K (oops i was off ;p)

the grid controls about that amount (560 uA) with about 1V variation. one may thus guess the µ is around 10.

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only one question, this FET has a max. input capacitance of 60pf, the output Z of the triode stage should be approx 18k, rough calculation says the HF rolloff should have the -3dB out at about 150kHz, just looking at the output on the scope while sweeping a sin wave through it, i seem to see the highs beginning to drop off at about 16k.

Any ideas?

Thanks for the interest though.

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- Calculate triode strapped characteristics from pentode data?