Help with MOSFET selection

[AudioGeek]

Here's what I am looking for:

A N channel power mosfet that is linear around 2A of Drain current and 40vdc supply voltage.

Bias voltage 2-4 volts or so.

will be running into a 64:8 Z transformer.

So far:

BUZ900P
2SK1529
2SK135

I think these are all lateral mosfets.

IS there an IR part that could work?

The attached image is of the output stage.

[AudioGeek]

Or there is the Exicon EC10N16/20 which looks very promising.

Any data sheets for this?

Thanks!

[Steve Eddy]

Looking to do a variation of Jean Hiraga's Nemesis amp?

se

[AudioGeek]

yes i am.

simulates good with a p channel buffer mosfet driving the n-channel stage.

good for 12W RMS into 8 ohms.

power supply thinking of:

33V/5A transformer
100v/50A bridge rectifier
2 50v/10,000uf caps
2mH air core inductor
then 2 50v/10,000uf caps

per channel

The p-channel buffer will have its own pi filter taken from the above mentioned bridge.

comments?

[Mr Evil]

The Exicon MOSFETs are nice. They do have datasheets on their website, although they contain limited data.

I have a spice model for ECF20N25 which you may find useful. Maybe not the exact one you're looking for, but they all behave similarly. Exicon will probably send you more data if you ask them.

.SUBCKT  ECF20N25 1 2 3
**********************************************
*      Model Generated by PEDC               *
*Copyright(c) Power Electronics Design Centre*
*         All Rights Reserved                *
*   Power Electronics Design Centre          *
*   Dept of Elec & Electronic Engineering    *
*   University of Wales Swansea              *
*   Singleton Park                           *
*   Swansea SA2 8PP                          *
*   Tel : +44 (0)1792 295420                 *
*   Fax : +44 (0)1792 295686                 *
*   E-mail : pedc@swansea.ac.uk              *
**********************************************
* Model generated on Dec 9 1999
* MODEL FORMAT: SPICE Level 1
* External Node Designations
* Node 1 -> Drain
* Node 2 -> Gate
* Node 3 -> Source
*
*
*
*                                     O [1]
*                                     |
*                                     Z
*                                     Z Rd
*                                     Z
*                                 D2  |
*                           Cdg0  |\ || [9]
*                           |-||--| >|O---O-----|--------|
*                           |  [4]|/ ||   |     |        |
*               [2]   Rg    |    ||---|   Z    ---     __|__
*               0--/\/\/\/\-O----|| M1    Z    / \D1   _____
*                           |[7] ||---|   Z    ---       |Cds0
*                           |         |   Z     |        |
*                           |    Cgs0 |   |RDS  |        |
*                           |-----||--O---O-----|--------|
*                                     | [8]
*                                     | 
*                                     O 
*                                     |
*                                     Z
*                                     Z Rs
*                                     Z
*                                     |
*                                     O [3]
M1 9 7 8 8 MM L=1 W=1
* Default values used in MM:
* With the exception of Cgs0 the capacitances are 
* added externally
* Other default values are:
*   RS=0 RD=0 LD=0 CBD=0 CBS=0 CGBO=0
.MODEL MM NMOS LEVEL=1 IS=1e-32 CGSO=1.57e-9
+VTO=0.414 LAMBDA=0.104 KP=2.808
RS 8 3 0.191
D1 8 9 MD
.MODEL MD D IS=1.0e-32 N=50 BV=250
+CJO=1.54e-9 VJ=0.633 M=0.479
RDS 8 9 1e+06
RD 9 1 0.289
RG 2 7 13.3
* Drain Source capacitance Cds0
CAP1 9 8 403e-12
*************************
* Gate Drain capacitance Cdg0
CAP 7 4 25.6e-12
*************************
* Gate Drain Capacitance Cdgj0
* Modelled as a diode
D2 4 9 MDD
.MODEL MDD D IS=1e-32 N=50
+CJO=137e-12 VJ=0.7 M=0.5
*************************
.ENDS

[ingvar ahlberg]

A Nemesis project seems fun, output transformers are a pretty good idea.

IS there an IR part that could work?

IR only has HEXFETS in ther line today, i think something like the IRFP240 would work well if You can use a TO 247 device, as i recall the BUZ 900 is TO3 ? As r-d/s is of lesser importance with the ot the Magnatec devices could be an option. Has been hailed as very good and, i think, still carries TO 3 parts.

[AudioGeek]

i tried that model... its way off what a 2SK135 or equiv would be.

the ECN 10N16 line is supposed to be like the 2SK135 or the 2SK1058...

that is what I need.

[AudioGeek]

i don't think anything else will work... other mosfets get very non-linear around this operating point.

btw, whats the difference between the BUZ900 series and the Exicon 10N16 line???

the datasheets look identical.

[Steve Eddy]

Originally posted by AudioGeek
yes i am.

simulates good with a p channel buffer mosfet driving the n-channel stage.

Why do you need the buffer to drive it? Or are you just looking to use the buffer as a unity gain preamp?

power supply thinking of:

33V/5A transformer
100v/50A bridge rectifier
2 50v/10,000uf caps
2mH air core inductor
then 2 50v/10,000uf caps

per channel

The p-channel buffer will have its own pi filter taken from the above mentioned bridge.

comments?

Sure. Thought of using batteries instead of an AC supply?

se

[AudioGeek]

well... it will make driving it easier...

47K input impedance instead of 1K or so...

improves HF response etc...

also, by adjusting how much current i have through the P channel buffer... i may be able to have some distortion cancellation.

hmm... 3 12V batteries per channel.... at least 10A/h they are pretty large and expensive.

yes i have thought about it and have built a power follower (12v supply at 4.5A bias current)... best midrange i have EVER heard in a SS amp.

anyways....

should 33vac be enough for a 40v supply at 2A?