Revisiting some "old" ideas from 1970's - IPS, OPS

Hi Valery


Your ideas seem to me very interesting, especially about VAS stage, may I suggest that you try the 2SC1775/2SA872 for the IPS stage, and the 2SA1360/2SC3423 for the VAS or as a low power Driver stage.
As a drivers the 2SD669/2SB649 and as you post earlier the Sanken's for output.
I made a lot of simulations on different circuits and this combination *give me *the best results.

Best regards
 
Here's a single sided through hole version of CDC-VFA-SSC
 

Attachments

  • CDC-VFA-CCS 3D.PNG
    CDC-VFA-CCS 3D.PNG
    333.8 KB · Views: 828
  • CDC-VFA-CCS-2 TH Bottom.pdf
    38 KB · Views: 173
  • CDC-VFA-CCS-2 TH silk mirrored.pdf
    47 KB · Views: 195
Hi Guys,

Hopefully you see this sometime in the morning. Seems I need a little nudge in the right direction. Is the schematic in post 21 the correct one? If so are D2/D4 15v? Should I use BC550/560 or BC546/556 for the small transistors?

Thanks, Terry

D2/4 are 15V. I drew it up wit BC550/560 but either choice would likely be fine at 15V. The two TO-92 in the VAS section are 2n5401/5551 for the higher voltage.
 

Attachments

  • CDC-VFA-CCS-TH.pdf
    95.5 KB · Views: 248
Last edited:
Hi Valery


Your ideas seem to me very interesting, especially about VAS stage, may I suggest that you try the 2SC1775/2SA872 for the IPS stage, and the 2SA1360/2SC3423 for the VAS or as a low power Driver stage.
As a drivers the 2SD669/2SB649 and as you post earlier the Sanken's for output.
I made a lot of simulations on different circuits and this combination *give me *the best results.

Best regards

Hi Antonio,

Thank you for the info, but 2SA1360/2SC3423 are rather rare in my area, and 2SC1775/2SA872 are nice low noise Hitachi devices, but simply impossible to get here (even Mouser doesn't sell them).

However, in case you've got the SPICE models for 2SA1360/2SC3423 - could you please share them? It would be interesting to try some simulations.

Cheers,
Valery
 
Valery, how good is thermal stability of the circuit, especially thermal stability of VAS idle current?

Very valid question. I did not test this particular one, but I have heavily tested my other symmetric circuit - >THIS ONE<
It took some tens of seconds to settle, but then it stayed constant (keeping the OPS bias stable) - no problem.

We have provided a local heatsink for the VAS TO-126's. At 5-7mA VAS current it's not going to be a problem anyway, if someone is going to run it at, say, 15mA (e.g. for driving the MOSFETs directly) - it will take a bit longer to settle and it will run warmer for sure, but I don't expect any thermo stability issues.
 
Hi Antonio,

Thank you for the info, but 2SA1360/2SC3423 are rather rare in my area, and 2SC1775/2SA872 are nice low noise Hitachi devices, but simply impossible to get here (even Mouser doesn't sell them).

However, in case you've got the SPICE models for 2SA1360/2SC3423 - could you please share them? It would be interesting to try some simulations.

Cheers,
Valery

Off course Valery, here they are:

.model 2sc3423 npn IS=14f BF=130 VAF=50 IKF=300m BR=5.61 VAR=500 RB=10 RE=0.01 RC=0.8 CJE=5p VJE=0.7 MJE=0.5 TF=795.77p XTF=7 VTF=6 ITF=50m CJC=4.4p VJC=0.6 MJC=0.286 XCJC=0.5 TR=4n XTB=1.5 EG=1.11 XTI=3 FC=0.5

.MODEL 2SA1360 PNP IS=116.73f BF=147.48 VAF=100 IKF=78.684m ISE=297.72f NE=1.5511 BR=.77363 VAR=100 IKR=1.0217 ISC=26.92n NC=2.9970 NK=.49889 RC=4.5038 CJE=4.0176p MJE=.33333 CJC=6.287p VJC=.35 MJC=.26272 TF=344.39p XTF=84.382 VTF=7.0050 ITF=.11443 TR=10n

greetings
 
Hi Valery,

I'm almost finished. I have been meaning to ask this for a while. I see all the time folks using .1uF as the value for the decoupling caps. I order them 50 at a time but am constantly running out of them. Anything magical about that value? I have a bag full of .22uF caps. Can I use those in place of the .1u for decoupling?

Thanks, Terry
 
Hi Valery,

I'm almost finished. I have been meaning to ask this for a while. I see all the time folks using .1uF as the value for the decoupling caps. I order them 50 at a time but am constantly running out of them. Anything magical about that value? I have a bag full of .22uF caps. Can I use those in place of the .1u for decoupling?

Thanks, Terry

I always use 220nf.
 
Hi Valery,

I'm almost finished. I have been meaning to ask this for a while. I see all the time folks using .1uF as the value for the decoupling caps. I order them 50 at a time but am constantly running out of them. Anything magical about that value? I have a bag full of .22uF caps. Can I use those in place of the .1u for decoupling?

Thanks, Terry
H.Ott says that you should use the highest value available in the package size you choose.
He was specifically referring to SMD, but in my opinion the same philosophy applies to through hole.
On that basis, if the 220nF is physically the same size and lead spacing as the 100nF, then buy/use the 220nF.