Search found 5381 matches

by ed
Sat Apr 29, 2023 7:40 am
Forum: Solid State
Topic: even more lateral fets
Replies: 83
Views: 56443

Re: even more lateral fets

I did think that you have nothing to prevent the 15v gate to source voltage from being exceeded. Maybe a pair of 12v back to back zeners are worth considering. That occurred to me also! I looked up the datasheet, Vgs ±15V abs max. thanks both. After Nick pointed out the gate resistance at 9mhz I re...
by ed
Fri Apr 28, 2023 4:55 pm
Forum: Solid State
Topic: even more lateral fets
Replies: 83
Views: 56443

Re: even more lateral fets

I've been doing a bit more research and the web contains scant but varied info on driving fets with opamps. What I think I've found is that opamps on average don't like more that 500pf load, which puts my latfets right on the limit. I've been doing some spice sims and some models do show collapse wh...
by ed
Fri Apr 28, 2023 11:31 am
Forum: Solid State
Topic: even more lateral fets
Replies: 83
Views: 56443

Re: even more lateral fets

more thoughts... have read and re-read all the TI papers by Bruce Trump. No further enlightenment at the mo, other than my best guess is still a capacitive load. From the TI papers I've taken a hint and will reduce the feedback resistors, retaining the ratio, and also remove the 47u capacitor. I hav...
by ed
Thu Apr 27, 2023 3:01 pm
Forum: Solid State
Topic: even more lateral fets
Replies: 83
Views: 56443

Re: even more lateral fets

Thanks for looking At the moment I don't think I'm going to acheive much because something fundamental has changed since first switching on. At first I had a buzz, but it produced a valid output, both sine and square, and it played music..... now there is serious corruption. The output from the opam...
by ed
Thu Apr 27, 2023 2:19 pm
Forum: Solid State
Topic: even more lateral fets
Replies: 83
Views: 56443

Re: even more lateral fets

I'm unable to reproduce the conditions at first switch on...something has popped/changed

here is the 10k square at the output of the opamp with no power to the fet...
mofo 10k fet off.jpg
mofo 10k fet off.jpg (120.94 KiB) Viewed 5224 times
and here with power to the fet...
mofo 10k fet on.jpg
mofo 10k fet on.jpg (137.14 KiB) Viewed 5224 times
by ed
Thu Apr 27, 2023 11:37 am
Forum: Solid State
Topic: even more lateral fets
Replies: 83
Views: 56443

Re: even more lateral fets

more head scratching with respect to this circuit, same as the previous mofo except larger chokes and opa2134 instead of ltc1150... mofo cct.jpg here is the ouput from the opamp. With opamp powered but the fet unpowered with input shorted...this looks acceptable to me.. mofo opamp no fet.jpg here is...
by ed
Wed Apr 26, 2023 8:39 pm
Forum: Solid State
Topic: even more lateral fets
Replies: 83
Views: 56443

Re: even more lateral fets

I spent a lot of time trying to understand what constitutes a capacitive load and thought I'd avoided it...but... I suspect that might be the problem...

I'm going to cut the capacitors out of the feedback loop to see if it makes any difference....any further suggestions would be gratefully received..
by ed
Wed Apr 26, 2023 4:41 pm
Forum: Solid State
Topic: even more lateral fets
Replies: 83
Views: 56443

Re: even more lateral fets

a bit more.. I've taken the smps out of the chassis and I'm running one channel with the smps well away from the chassis. This is a shot of the input and output on the scope with the input shorted. The input trace has me well curious. If I put my hand on the chassis both traces go to a flat line for...
by ed
Wed Apr 26, 2023 8:58 am
Forum: Solid State
Topic: even more lateral fets
Replies: 83
Views: 56443

Re: even more lateral fets

waily waily..... major disappointment......plugged into the main system and switched on.....serious buzz.... scratched head a bit... took out the earth lift for the balanced supply to the audio circuit, bearing in mind that the meanwells only have chasis ground direct to the incoming earth point. So...
by ed
Tue Apr 25, 2023 6:19 pm
Forum: Solid State
Topic: even more lateral fets
Replies: 83
Views: 56443

Re: even more lateral fets

bit more....

got it running in biased at 2 amps
here's the square wave at 10k.....
mofo sq1a.jpg
mofo sq1a.jpg (129.72 KiB) Viewed 5360 times
at this point it clips at 2.52v i/p - 6.74v o/p - 5.67 watts
by ed
Mon Apr 24, 2023 1:07 pm
Forum: Assorted Stuff
Topic: General health matters.
Replies: 784
Views: 190214

Re: General health matters.

It's all a bit other worldly to me at the mo because the surgeon explained that for those people that wear glasses there is often no need to wear them after the op. In my case I was astounded because I was losing sight in my left eye(very suddenly since Christmas) which was not caused by the catarac...
by ed
Mon Apr 24, 2023 12:59 pm
Forum: Assorted Stuff
Topic: General health matters.
Replies: 784
Views: 190214

Re: General health matters.

+1

I've just had my left lens replaced, which has restored the sight in that eye. Waiting for things to settle before the work on my right eye. I deffo consider this a fix.
by ed
Mon Apr 24, 2023 12:37 pm
Forum: Assorted Stuff
Topic: Nothing In Particular
Replies: 16439
Views: 4649902

Re: Nothing In Particular

RE: the national mobile telephone emergency alert not really in a position to comment because I don't have a mobile phone..but.... the mem sahib didn't receive an alert so after the BBC discussions I checked her phone and lo and behold there is a switch that has to be turned on to allow such alerts ...
by ed
Sat Apr 22, 2023 6:46 pm
Forum: Your Fave Artists
Topic: What Are You Listening To Right This Minute?
Replies: 6152
Views: 1874663

Re: What Are You Listening To Right This Minute?

IslandPink wrote: Sat Apr 22, 2023 5:14 pm
shane wrote: Fri Apr 21, 2023 9:03 pm How is it 45 years?
Amazing, but time has a sneaky habit of creeping up on your arithmetic.
snigger
by ed
Sat Apr 22, 2023 3:37 pm
Forum: Assorted Stuff
Topic: Nothing In Particular
Replies: 16439
Views: 4649902

Re: Nothing In Particular

<pedant mode> not sure of the benefit here. Apart from the marketing confusion where some suppliers are now advertising batteries in mwh instead of the original method of mah...it could mislead some. these batteries have a capacity of about 330 mah compared to cheap dry batteries of about 400 mah. I...