Search found 5381 matches

by ed
Fri May 05, 2023 9:05 pm
Forum: Assorted Stuff
Topic: Interesting (non musical) YouTube videos.
Replies: 413
Views: 148587

Re: Interesting (non musical) YouTube videos.

it's no longer star wars day
by ed
Fri May 05, 2023 2:59 pm
Forum: Solid State
Topic: even more lateral fets
Replies: 83
Views: 56457

Re: even more lateral fets

I think this will be safe now...
it's still relatively simple
please shout if I've missed something...I do seem to be missing some obvious things lately.
also..can some kind soul confirm that q2 and q3 don't have to be matched and could be common or garden npn
mofo5 cct.jpg
mofo5 cct.jpg (121.59 KiB) Viewed 7304 times
by ed
Fri May 05, 2023 8:56 am
Forum: Solid State
Topic: even more lateral fets
Replies: 83
Views: 56457

Re: even more lateral fets

I would agree with Mike on the current source. Not sure why using a current mirror would be preferable to just a simple two transistor current source, or just a jfet CCS. Unless I guess you want the current to vary with the supply rails which the mirror will do. Unless there is some reading I shoul...
by ed
Fri May 05, 2023 8:00 am
Forum: Your Fave Artists
Topic: How could anybody be THAT good at ANYTHING ??
Replies: 153
Views: 141851

Re: How could anybody be THAT good at ANYTHING ??

wow
now where've I heard those scales before..bet he's a Zappa fan.
but yeah, a fine bit of noodling.
by ed
Thu May 04, 2023 1:05 pm
Forum: Solid State
Topic: even more lateral fets
Replies: 83
Views: 56457

Re: even more lateral fets

to elaborate on the issue of matching in the current mirror. I got most of my background from the analog tutorials and the apnote for the current mirror under an emitter follower recommends ssm2212. I couldn't find a spice model at the time so just used a pair of ubiquitous 3904s thinking it would b...
by ed
Thu May 04, 2023 9:40 am
Forum: Solid State
Topic: even more lateral fets
Replies: 83
Views: 56457

Re: even more lateral fets

I'm now at a crossroads. In spice I can't find any simple improvement over my emitter follower with a current mirror as shown in post #49. Notwithstanding my senior moment of feeding a non centred square wave, the spice output for the whole circuit looks ok ish with proper square wave input. so...do...
by ed
Thu May 04, 2023 8:36 am
Forum: Assorted Stuff
Topic: Interesting (non musical) YouTube videos.
Replies: 413
Views: 148587

Re: Interesting (non musical) YouTube videos.

It's star wars day...whoopeee!
by ed
Tue May 02, 2023 1:39 pm
Forum: Solid State
Topic: even more lateral fets
Replies: 83
Views: 56457

Re: even more lateral fets

My bad!! please read my sentence to be 'some people refer to it' rather than 'some people consider it' further with the dc and square wave , I realise now that I wasn't feeding it a balanced square wave. I have now woken up a bit and realise that even if I get spice to supply a balanced square wave ...
by ed
Tue May 02, 2023 1:30 pm
Forum: Solid State
Topic: even more lateral fets
Replies: 83
Views: 56457

Re: even more lateral fets

can anybody elaborate on this behaviour Caps don't pass DC, so I don't see why you would expect anything different. The output is ramping towards a net DC value of 0v. many thanks... I wasn't aware that a square wave was considered to have a dc component...but having read some more I see lots of pe...
by ed
Tue May 02, 2023 11:39 am
Forum: Solid State
Topic: even more lateral fets
Replies: 83
Views: 56457

Re: even more lateral fets

ah ha...there's more
with the coupling cap I get this...
xxxxxx.jpg
xxxxxx.jpg (181.65 KiB) Viewed 6181 times
and without the coupling cap the output follows the input correctly.
I'm at the limit of my understanding now.....can anybody elaborate on this behaviour?
by ed
Tue May 02, 2023 8:18 am
Forum: Solid State
Topic: even more lateral fets
Replies: 83
Views: 56457

Re: even more lateral fets

I think I may have found the answer to the question above. It may be down to stray capacitance in the bjt load resistor. in my case I currently have 3 resistors in parallel to minimise heat and avoid another heat sink. I don't fully understand the principal but I'm creeping up on it. mm..replace the...
by ed
Mon May 01, 2023 7:57 pm
Forum: Solid State
Topic: even more lateral fets
Replies: 83
Views: 56457

Re: even more lateral fets

continuing to play with emitter follower...
bjts, nasty little things, just like hobbitses
the output cap does modify it slightly but the behaviour remains
has anybody seen this behaviour before, or suggest possible reasons for it?

10k sq.jpg
10k sq.jpg (226.88 KiB) Viewed 6239 times
by ed
Mon May 01, 2023 8:35 am
Forum: Solid State
Topic: even more lateral fets
Replies: 83
Views: 56457

Re: even more lateral fets

grrrr grrrr grrr.....it's almost like you guys are in my head.. for the last 2 days I've been doing the mental gymnastics with exactly the thoughts just mentioned... I've simmed every buffer method I can think of but they all add complication and extra circuit in the path. I started with the simple ...
by ed
Sat Apr 29, 2023 3:18 pm
Forum: Solid State
Topic: even more lateral fets
Replies: 83
Views: 56457

Re: even more lateral fets

if you bias the hpa correctly at about 1/2 V+ which will be 6v bias with a 12v v+ That's a good point actually - just to be sure the trimmer needs adjusting so the gate's at 6V? no, not exactly....the trimmer needs adjusting so that there is 6v on the source pin, which is sitting on top of the load...
by ed
Sat Apr 29, 2023 10:31 am
Forum: Solid State
Topic: even more lateral fets
Replies: 83
Views: 56457

Re: even more lateral fets

weeel...anything can happen in the next half hour... but seriously....different scenario to the opamp output.... if you bias the hpa correctly at about 1/2 V+ which will be 6v bias with a 12v v+ then you would have to i/p about 5-6v RMS signal to get the peak voltage into the gate at near max. That ...