End of an Era for TO3 Lateral MOSFETs - UK Vintage Radio Repair and Restoration Discussion Forum

knobtwiddler · 3rd Nov 2022, 11:20 am

https://www.profusionplc.com/news/en...teral-mosfets/

Ok, a few months back, but I just caught it. There must be quite a few here who built Maplin MOSFET amps (just one example)?

I feel a little sad at reading the news, but I can't quite figure out if it's because a chapter of my youth feels to have truly closed (I use LM amps to this day and have the test kit to verify how good they are), or whether the T03 package is going to make any objective difference... It will dissipate more heat than a plastic package, so you can get more bias out of the same device. You can parallel plastic devices if you need to put more bias into them. But considering how good Class D amps now are (witness Hypex or Benchmark Media), and how much more efficient they are (with the bias switch up high, my MOSFET amps help heat the room...), should anyone mourn the passing of T03 MOSFETs?

kalee20 · 3rd Nov 2022, 12:30 pm

Reading this, the plastic (TO247) devices are still being continued, thus the bare chips are still made.

It wouldn't be impossible to get a packaging company - Semelab* comes to mind - to package them in TO3. Sure, there's be minimum-quantity charges, but it's not impossible.

* I have to declare an interest, as Semelab, and the company I work for, are part of the same group of companies.

McMurdo · 3rd Nov 2022, 12:55 pm

The mosfets in the link are already made by TT Electronics (semelab)

G6Tanuki · 3rd Nov 2022, 4:20 pm

Definitely end of an era.

I similarly mourn the passing of the likes of the VMP4, which could provide several Watts of HF/VHF linear amplification and also found a place in 'bomb proof' receiver front ends where you were sharing a mast with pager transmitters or a local FM broadcast TX.

Radio Wrangler · 3rd Nov 2022, 7:05 pm

I had a few VMP4 samples sitting in my desk drawer for years, then Colin Horrabin was looking for some to have a play with high dynamic range RF and IF amplifiers, so they went to him. Quite fruity devices.

David

John_BS · 3rd Nov 2022, 8:09 pm

They're also used in the front end of the BBC's FM rebroadcast receivers ....
John

Radio Wrangler · 4th Nov 2022, 12:45 am

I'm not surprised.

There are some RF LDMOS devices that could be used as alternatives. If you get handed the poison chalice to modernise the thing, avoid MRF1513 like the plague. right power level, loads of bandwidth, dodgy stability. Note that the datasheet is for a device with an RC section added to the gate.... If that doesn't worry you, nothing will.

David

3rd Nov 2022, 11:20 am	#1
knobtwiddler Octode Join Date: Mar 2016 Location: London, UK. Posts: 1,047	End of an Era for TO3 Lateral MOSFETs https://www.profusionplc.com/news/en...teral-mosfets/ Ok, a few months back, but I just caught it. There must be quite a few here who built Maplin MOSFET amps (just one example)? I feel a little sad at reading the news, but I can't quite figure out if it's because a chapter of my youth feels to have truly closed (I use LM amps to this day and have the test kit to verify how good they are), or whether the T03 package is going to make any objective difference... It will dissipate more heat than a plastic package, so you can get more bias out of the same device. You can parallel plastic devices if you need to put more bias into them. But considering how good Class D amps now are (witness Hypex or Benchmark Media), and how much more efficient they are (with the bias switch up high, my MOSFET amps help heat the room...), should anyone mourn the passing of T03 MOSFETs?

3rd Nov 2022, 12:30 pm	#2
kalee20 Dekatron Join Date: Feb 2007 Location: Lynton, N. Devon, UK. Posts: 7,081	Re: End of an Era for TO3 Lateral MOSFETs Reading this, the plastic (TO247) devices are still being continued, thus the bare chips are still made. It wouldn't be impossible to get a packaging company - Semelab* comes to mind - to package them in TO3. Sure, there's be minimum-quantity charges, but it's not impossible. * I have to declare an interest, as Semelab, and the company I work for, are part of the same group of companies.

3rd Nov 2022, 12:55 pm	#3
McMurdo Dekatron Join Date: Jun 2009 Location: Staffordshire Moorlands, UK. Posts: 5,271	Re: End of an Era for TO3 Lateral MOSFETs The mosfets in the link are already made by TT Electronics (semelab) __________________ Kevin

3rd Nov 2022, 4:20 pm	#4
G6Tanuki Dekatron Join Date: Apr 2012 Location: Wiltshire, UK. Posts: 13,998	Re: End of an Era for TO3 Lateral MOSFETs Definitely end of an era. I similarly mourn the passing of the likes of the VMP4, which could provide several Watts of HF/VHF linear amplification and also found a place in 'bomb proof' receiver front ends where you were sharing a mast with pager transmitters or a local FM broadcast TX. __________________ I'm the Operator of my Pocket Calculator. -Kraftwerk.

3rd Nov 2022, 7:05 pm	#5
Radio Wrangler Moderator Join Date: Mar 2012 Location: Fife, Scotland, UK. Posts: 22,874	Re: End of an Era for TO3 Lateral MOSFETs I had a few VMP4 samples sitting in my desk drawer for years, then Colin Horrabin was looking for some to have a play with high dynamic range RF and IF amplifiers, so they went to him. Quite fruity devices. David __________________ Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done

3rd Nov 2022, 8:09 pm	#6
John_BS Octode Join Date: Dec 2008 Location: Wincanton, Somerset, UK. Posts: 1,780	Re: End of an Era for TO3 Lateral MOSFETs They're also used in the front end of the BBC's FM rebroadcast receivers .... John

4th Nov 2022, 12:45 am	#7
Radio Wrangler Moderator Join Date: Mar 2012 Location: Fife, Scotland, UK. Posts: 22,874	Re: End of an Era for TO3 Lateral MOSFETs I'm not surprised. There are some RF LDMOS devices that could be used as alternatives. If you get handed the poison chalice to modernise the thing, avoid MRF1513 like the plague. right power level, loads of bandwidth, dodgy stability. Note that the datasheet is for a device with an RC section added to the gate.... If that doesn't worry you, nothing will. David __________________ Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done