50w Single-Ended BAF2015 Schade Enabled

[generg]

He sez, but first time no picture,

First picture comes from 2picodumbs......)

 

[2 picoDumbs]

there is (in Babelfish J and pretty much every second amp on planet) inherent servo (input LTP) which is taking care of output offset , via NFB

you don't have that in mumbojumbopuckamp

though, if Papa sez and shows it's doable , no reason for doubts

True.
I think Generg's biasing circuit achieves somewhat similar effect, but I don't know if Papa intended to do it that way based on his schematic.
Either way, I'm a sucker for punishment, so I'll do it exactly how Papa has drawn it to start with.

 

[Soundhappy]

He sez, but first time no picture,

First picture comes from 2picodumbs......)

 

[2 picoDumbs]

Constructed opto coupled current source half of circuit.
I'll test it tonight.

 

[2 picoDumbs]

Was on the toilet and another idea came.
I'll be back in 5 hrs with the circuit.

 

[generg]

Great place, big ideas!

Good luck!

 

[RobLK]

Great place, big ideas!

Good luck!

Could be that he could think more clearly once he relaxed and got a load off his mind.

 

[2 picoDumbs]

Someone needs to do a PhD thesis on this phenomenon.

 

[RobLK]

So Picodumbs, did you change your mind about trying the stock circuit?

 

[2 picoDumbs]

[special=]%[/special]

So Picodumbs, did you change your mind about trying the stock circuit?

No. I will still try the most basic circuit to satisfy my own curiosity.

 

[2 picoDumbs]

Cat Skin Mk42a

Another cat skin.
This is the fruits of spending time on the toilet. Hahahahaha


R16 is a 5k trimpot (wiper shorted)

 

[2 picoDumbs]

Testing of Optocoupled CCS Part 1 Complete

Completed optocoupled ccs circuit on breadboard, all is functional. Mosfet turns on nice and slow.

With R5=20k I am getting approximately 2.7A.
I can do a short video showing soft turn on of circuit.

Next stage, I will test for stability of CCS over extended period as heatsink warms up. This shouldn't need further testing but I will do it for the low in faith, and curiously minded people.

The test circuit is below.

 

[2 picoDumbs]

Here is video, showing turn on behaviour of CCS circuit.

https://www.youtube.com/watch?v=BPKOTdmNhQ8

 

[2 picoDumbs]

After monitoring CCS for 1 hour it is rock solid stable, as expected.

I'll retest with R5=15K

 

[2 picoDumbs]

R5=20k 2.74A
R5=15k 2.83A
R5=10k just starting to hit current limit of lab suppy at 2.95A. I'll pull out a 30V switching supply and test.

 

[Soundhappy]

Congratulations Pico and thanks for interesting video

 

[RobLK]

Yes nice video, thanks much Pico. It's good to see that it is behaving well.
Now I'm excited to see how it will behave in the complete circuit, I hope it works.
Some others had problems with it so maybe thier problem was in the other part of the circuit. Maybe something was feeding back and causing problems.

 

[RobLK]

Simulating your test circuit in Ltspice using an IRFP250n gave me very similar results to your measurements. I had to go down to 7k ohms to get 3.2 amps.

 

[2 picoDumbs]

Update

Now tested with 30V supply without current limiting.

With R5=10k, I'm getting a stable 3.06A

Changing R1 and R2 to 0.56Ohms gets me to 3.14A, so in the ball park of where Papa said it should be.

I'll build the rest of the circuit to see how it behaves.

 

[mr_whocares]

Now tested with 30V supply without current limiting.

With R5=10k, I'm getting a stable 3.06A

Changing R1 and R2 to 0.56Ohms gets me to 3.14A, so in the ball park of where Papa said it should be.

I'll build the rest of the circuit to see how it behaves.

we are all impatiently waiting for your results