Spice Models for 2SC4001 and 2SA1546

Try Class AB, a lot cooler.

Graham Holloway WPS Electronics

Ho humm....this was a bit of a joke of course!

The circuit is in already class B, i.e. as small a bias as possible. It runs fine at 20kz, at 1Mhz its smoking due to switching losses. You need about 2-4A drive to get down to 10ns. This cant be done practically. Anything that gives 1A out, needs around 1A in at 10ns, at these voltages (think "ft" of 100Mhz).

Kevin Aylward snipped-for-privacy@anasoft.co.uk

So was my comment. Although there is a yahoo class A group that would welcombe you with open arms, suggestions of water cooling, etc, if you should choose that route.

Most designers of power amplifiers have seen this problem, but I suspect they have just decided to compromise on the amount of drive they want to use against what constitutes a reasonable upper frequency limit. For example, in the case of audio, how much energy is really present at the higher frequencies?

If you really want a 500W square wave at 1MHz you really have no choice but to find a way of generating the gate drive. I'm sure lots of suggestions will come in.

For a pro audio power amp, i.e. one that can have syths cymbals etc, and all sort of stuff, one wants to have full power capability at 20Khz to avoid any potential of I.M.D. For example, one might be using a 100W amp flat out just for the horns covering say, 3k-20k, in a system of 500W for the low end. From a practical point, my view is that the design goal is full power at 40Khz to give some margin. Of course, if the amp is used with wideband cd music, its unlikely to require full output at 20k, but one has to design such that the amp can be used for *any* audio application.

If an amplifier does start triangling at say, 15Khz, its a sure bet that that even at lower levels the amp has a fair amount of imd. Fast amps and low hf distortion go hand in hand. Its not that you need such a fast slew, but those that dont usually have higher distortion.

This is simply a theoretical exercise.

I wasn't asking for any. I know how. Its cost that is the issue.

Kevin Aylward snipped-for-privacy@anasoft.co.uk