Sub for 2SK2961 or 2SK975 MOSFET

[jbau]

I have a headphone amp that uses a couple of these to drive the transformer in a DC-DC converter. Like so many TH components, these low-power Mosfets are no longer made. Key spec seems to be the low on-resistance (0.3-0.4 Ohms).

I've never spec'ed mosfets before so I wanted to get some input. Two possible replacements are Vishay VISHS85750 and Diodes Inc/Zetex ZVN4306AV.

Wha'dya think?

 

[jbau]

Ooops, forgot to attach the 2SK975 data sheet.

 

[dliscomb]

I assumed the data sheet has a typo; "Rds(off)" should be "Rds(on)"

My concern is more the power dissipation. Over 800mw in a TO-92 package is pretty rare these days (perhaps always?), based on my spelunking with the Digikey search tools. I only got 2 hits for
* MOSFET
* N-channel
* TO-92 package
* over 900mA Id
and they were the Diodes Inc. ZVN4306 and ZVN4310. Maybe 850mW would suffice.
Hard to tell how close they were designing it without a schematic or some measurements. A 60V-rated part in an HPA?

These days, they seem to use TO-220 package.

Kind regards,
Drew

 

[jbau]

Thanks Drew. Yeah, offerings in the 92L package are pretty much gone and I don't think there's room for a TO-220, it's a pretty dense layout. I used 1A Id and <500mOhm Rds(on) for my scan, with only two results. I ordered some of the ZVN4306 from Digikey but USPS appears to have lost the package.

Last night I found another possibility in one of my junk boxes, some IRFU110's (TO-251).

Schematic is attached (Q31 and Q32).

 

[dliscomb]

Mouser has a few more options.

 

[jbau]

The ZVN4306 's arrived yesterday, along with a new SG3524. These ZVN's are the little "Eline" package, which may explain the low power rating. We'll see if they hold up.

 

[jbau]

Just to wrap this up, the ZVN4306's are working fine, so a good sub for the K975 (note the different lead pinout, though).

 

[dliscomb]

Super! Thanks for the follow-up jbau!
Kind regards,
Drew