help to find mosfet

Hi all,

I would like to try building my first audio power amplifier “push/pull”.

Could you recommend a “good” pair of Mosfet endings (channel p and channel n)? (where “good” = easily available, not oversized and with (LT)Spice model).

The amplifier will look like this: P=25Wrms, load 8ohm and Vpwr = +/- 35V.

Thank you all!,
Marco.
 

Mooly

Administrator
Paid Member
2007-09-15 8:14 am
Welcome to diyAudio Marco :)

You are going to get lots of different opinions over this.

Size isn't really negotiable since you will be looking at either flat packaged devices (TO247 outline) or round TO3 outline. Flat is easier to work with as they only need one hole drilling.

If you choose the common vertical HEXFET then you are looking at the IRFP9240 and IRFP240 type or there derivatives. LT spice has models built in for those.

My favourite devices for a small amplifier would be the less common Lateral FET which are available from certain suppliers. LTspice models are available on this forum from Bob Cordell and Ian Hegglun. A quick search will bring them up.
 
Welcome to diyAudio Marco :)

You are going to get lots of different opinions over this.

Size isn't really negotiable since you will be looking at either flat packaged devices (TO247 outline) or round TO3 outline. Flat is easier to work with as they only need one hole drilling.

If you choose the common vertical HEXFET then you are looking at the IRFP9240 and IRFP240 type or there derivatives. LT spice has models built in for those.

My favourite devices for a small amplifier would be the less common Lateral FET which are available from certain suppliers. LTspice models are available on this forum from Bob Cordell and Ian Hegglun. A quick search will bring them up.

I have used irfp240/9240 with good results.

Exicon and Profusion do lateral mosfets but expect to pay through the nose for them compared to irfp240/9240.
 
Yes. My LTspice models turned out to be almost identical using the same manufacturers datasheets. The thermal values are different, obviously, due to their cases.

For TO-220's adding an Al spreader plate of slightly more area than the TO-247 will help somewhat (otherwise you will need more heatsink with TO-220's else reduce the amps power). Use thermal pasted between the TO-220's and the plate with no thermal washer. Then use the larger thermal washers between plates and HS :cool:..

BTW If there are paralleled devices with common drains then a common spreader can be used for the N's and another for the P's. Then cut your own massive washers from sheet. I think it's still available from the DIYaudio store.