LF: : Alternatives Re: STW34NB20 - STW70N60M2?? Jays response

[Laurence KL7 L <hellozerohellozero@hotmail.com>]

Thanks Jay - Yep its a concern especially having read and digested your warnings on changing to higher gate capacity devices, but Im only going to use the new FET devices, or at least test them,   in the 500W mode which I should have indicated -  so with just two FETS and reading the application notes the 2110 hopefully  will be adequate at 475kHz to drive into the combined gate load. Ill know pretty quickly -
 
I read the blog http://tahmidmc.blogspot.com/2013/01/using-high-low-side-driver-ir2110-with.html which contains a load of additional info and one of the directives this guy had is to strap a 1K ohm resistor between the Gate and  (source)deck to stop unwanted ONs (big bangs) due to potential floating gate charges and or Miller effects etc; wonder what your thoughts are there and in your design are the devices considered to be driven as a low side and therefore each FET could have a 1K inserted as insurance or are they pseudo in parallel (don't think so) in which case the R value would be 2K etc. The guy writes quite well..
 
The Alaska permanent dividend (oil) fund (1884 bucks this year ) funded this experiment :-) ps do you have any 79 material left?
 
thanks again for the support
 
ps overnight just West coastish paths openings on WSPR2 - Im sure we will cross the West East barrier sooner or later...a lot of the stations were suffering from Tstorms or for KH6 hurricane warnings -
 
Laurence KL7L
 

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From: jrusgrove@comcast.net
To: rsgb_lf_group@blacksheep.org
Date: Tue, 14 Oct 2014 07:31:56 -0400
Subject: LF: Re: Alternatives Re: STW34NB20 - used in a number of MF and LF PA designs

Laurence

 

At over twice the input capacitance expect my driver circuit to come up short ;~( .

 

Jay W1VD  WD2XNS  WE2XGR/2 

----- Original Message -----

From: Laurence KL7 L

To: rsgb_lf_group@blacksheep.org

Sent: Monday, October 13, 2014 8:15 PM

Subject: LF: Alternatives Re: STW34NB20 - used in a number of MF and LF PA designs

STW70N60M2  600V VDs  0.031 Ohm on and Imax as 68A  - Ill let you know how they work in cct but it looks like completely over the top Gold over engineered FET device but I need the insurance give the changes and sudden animal interventions/weather I get up here in Alaska -
 
http://www.mouser.com/ProductDetail/STMicroelectronics/STW70N60M2/?qs=Rlwi1sSxVL4hmaII3E%2FvIA%3D%3D
 
I  temp switched over to a 600V FET, the end of life or about to be http://www.mouser.com/ProductDetail/STMicroelectronics/STW16N65M5/?qs=sGAEpiMZZMutXGli8Ay4kNbVQor0Njej2JFFy%252bQzHzg%3d
 
this is a "smaller" I tot device and gets a little warmer than more lower Ron ohms 34NB20 but was running fine in 1Kw W1VD design with no change in tap points out optimizing the Voltage/Current ratios.... I have a pair of them at 300W out and effieciency was about 72% or so. I didnt see any peaky waveform on the drains either..
 
All being well Ill be on WSPR2 630m tonight - weather up here is far too warm - lake ice has melted  and the ducks and Swans are back enroute South
 
Laurence KL7L