Passlabs X1000 output stage driven by a To264 transistor?

[Zen Mod]

counting on fact that I'm having two left legs , am I more of Circlotron , than true complementary type?

[PRR]

Originally Posted by rhythmsandy

But have you used a TO 264 .... in general what is the way to overcome the capacitances.... Just increasing the driver idle current will suffice?

Capacitance is like a Mass. In audio we need to move that mass quickly.

Say you need fast delivery of cargo anywhere from Peterborough to Folkstone (anywhere between two points).

If the cargo is 2-hand size, you can use a moped. Engine the size of a loaf of bread.

If it is a Ton, you need a pickup truck. Engine like a dresser.

If it is say 500 Tons, you need something even larger. Engine the size of a chicken-shed. Heat-sink (radiator) so big you need a stairway to get to the top.

[rhythmsandy]

Originally Posted by Nelson Pass

There were no bipolar transistors in the amplifier.

If you go through PRR's analysis you see that the capacitance is not
nearly as much as you might imagine. The Cgd is the one that piles up
on you when you parallel lots of devices.

How do we overcome the effect of Cgd. Consider a 100W or 200W F5 to be built as the current F5 Turbo has got about 4 pairs of mosfets and I believe they are driven by a toshiba To220 package transistors. How many mosfets in total a 2sc4793 can drive without any issues. Secondly how is the stability wrt oscillations when paralleling 10 or pairs of mosfets.

[Nelson Pass]

The bipolars in the F5 Turbo are cascodes. In my book they only count
for shielding the Jfets from voltage, and don't really affect the drive to
the output devices.

But your question nicely segues into another point worth making -

"How do we overcome the effect of Cgd."

Cascoding is an excellent way to remove Cdg and Cds. To the extent
that Vds, Vdg are held constant by a cascode, you are not charging
those capacitances.

[rhythmsandy]

Cascoding the VAS output or drivers?

[Nelson Pass]

Output devices.

Like in the CAS1 and CAS2

[rhythmsandy]

then we need alot of output devices in that case way too higher but is it the way its implimented in x1000?

Looking at the A75 amp the massive output stage was driven with IRF9610 and IRF610 were they sufficient to drive them?

[Zen Mod]

fact: they made it

fact: they published schematic in article

fact: many made it from schematic

fact : substancial number of specimens is working today still , on owners happiness

so , what could be answer to your question?

go read a book or two , you can even download them for free

[Nelson Pass]

Originally Posted by rhythmsandy

Looking at the A75 amp the massive output stage was driven with IRF9610 and IRF610 were they sufficient to drive them?

What is your criteria for "sufficient"?

[rhythmsandy]

Well produced 100Khz Squarewave instead of distorted because of unable to drive the non linear capacitance from OPS. Not by the IPS or VAS.