[Eeyore]

Proof is a nice, closed form mathematical solution. A simulation may
only be sufficiently consistent with or essentially inconsistent with
the math (or else uninterpretable.)

I'll be more pedantic. It should have read " a good simulation ought to
illustrate this ".

Graham

 

[Eeyore]

This is part of why you always see the harmonics near the gain
crossover point point.

I'm not familiar with this term " gain crossover point ". Could you elaborate ?

Graham

 

[Fred_Bartoli]

Eeyore a écrit :

I like the idea of the rigid mathematical anyalsyis too actually. A simulation
using a SPICE based tool is just so much quicker.

But it covers only one case. And gives you almost no insight WRT to the
system behaviour when parameters vary, unless you put considerable
efforts in this.
Analytical modeling along with proper simplifications gives you all that
at once.

 

[PeteS]

There are some BGA mosfets, tiny packages with absurdly low Rds-on
values.

John

There are some IR devices with pretty low Rds-on specs - see the IRF6620
for instance (2.7 milliohm @ 10V and 28nC typical gate charge). I've
used these things in high current supplies and the efficiency you can
squeeze out is pretty astounding. (The device for sync is the 6623)

Philips (now NXP) has a line of P-channel devices with astounding (for a
P-channel device) rds-on, the number of which escapes me right now - it
was about 10 milliohm @ 5V.

I used a BGA driver + FETs from IR a while back that had pretty decent
specs too.

Cheers

PeteS

 

[[email protected]]

A good simulation ought to prove this.

Graham

I'm probably stating the obvious for reader of this list, but when
harmonic analysis is used in spice, you need to insure the time step
is uniform, that is, use all the parameters on the .tran line. I make
the time step fall on an integer divider of the period of the sine
test source.

Spice really isn't all that good for very subtle effects, i.e. it is
only as good as the models, plus spice doesn't conserve charge.