SSA is completely different situation.
You have to read post #80 in this thread where I explained all three different possibilities to inject input bias current at this CFB topology. VSSA is different because current injection resistor is in between two AC grounds, so AC voltage drop on it is zero. DC voltage drop is high and almost constant so current is therefore constant as it would be CSS. See the idea ...
Yes i know. But it is basicly the same, the path is the same and only difference is that the emitter feedback resistors are ac versus dc coupled.
But what sounded Best on the ssa??? Dig into your memory and notes , Then you know what you should do.
I am know what i would do. The TSSA performs very Well with the ccs.
SSA is completely different situation.
You have to read post #80 in this thread where I explained all three different possibilities to inject input bias current at this CFB topology. VSSA is different because current injection resistor is in between two AC grounds, so AC voltage drop on it is zero. DC voltage drop is high and almost constant so current is therefore constant as it would be CSS. See the idea ...
Bjt + jfet CCS will dynamicly have a zout of >1meg compared to 15k for the resistors . So dynamicly less bias current modulation.
As you know SSA has very capable CCS installed and overal performance is on top level.
TSSA has AC voltage drop on injection resistor which is as high as input voltage or as divided feedback voltage, so injection current is far from being constant. CCS is essential in TSSA.
VSSA has zero AC voltage drop on injection resistor.
I really decided to explore this basic CFB topology to the extreme, all combinations, all versions build, tested and listened to.
TSSA has AC voltage drop on injection resistor which is as high as input voltage or as divided feedback voltage, so injection current is far from being constant. CCS is essential in TSSA.
VSSA has zero AC voltage drop on injection resistor.
I really decided to explore this basic CFB topology to the extreme, all combinations, all versions build, tested and listened to.
hey, we are happy with anything that works well
going for the best is a different story
we know how that goes...it never ends
I personally hope it will be kept close to the present state where proto board and hardwire is still possible
any chance to use available drivers, instead of 'obsolete' devices ?
going for the best is a different story
we know how that goes...it never ends
I personally hope it will be kept close to the present state where proto board and hardwire is still possible
any chance to use available drivers, instead of 'obsolete' devices ?
So dynamicly less bias current modulation.
If AC voltage drop on resistor is zero, where's current modulation than?
As you know SSA has very capable CCS installed and overal performance is on top level.
TSSA has AC voltage drop on injection resistor which is as high as input voltage or as divided feedback voltage, so injection current is far from being constant. CCS is essential in TSSA.
VSSA has zero AC voltage drop on injection resistor.
I really decided to explore this basic CFB topology to the extreme, all combinations, all versions build, tested and listened to.
Which resistors are thinking of when you say injection?
It is going to be a busy night.
No AC on resistor means no current modulation. Why do you think all SIM-s at the beginnig of this thread showed H2 -100dB with current injection resistor only? No AC - no modulation - constant current. Resistor only makes it, just imagine what would happen if we go complex on VSSA. CCS would rocketed performance to -130dB and less.
Which resistors are thinking of when you say injection?
It is going to be a busy night.
In VSSA sch both 15k are input stage's current injection resistors, located between two AC grounds. Feedback AC ground enabled with 10uF plus 2,2mF, rails AC ground enabled with all capacitors to GND, ripple in front-end set to minimum as we use resistor-diode-capacitor-GND serial link.
hey, we are happy with anything that works well
going for the best is a different story
we know how that goes...it never ends
I personally hope it will be kept close to the present state where proto board and hardwire is still possible
any chance to use available drivers, instead of 'obsolete' devices ?
What i mention has no impact on steady State values tinitus. This means that you Can still hardwire it with a resistor instead
any chance to use available drivers, instead of 'obsolete' devices ?
Yes, if they're capable as the ones from sch. Not so easy task these days.
In VSSA sch both 15k are input stage's current injection resistors, located between two AC grounds. Feedback AC ground enabled with 10uF plus 2,2mF, rails AC ground enabled with all capacitors to GND, ripple in front-end set to minimum as we use resistor-diode-capacitor-GND serial link.
Know i see it. Correct the currentsource with the 15k is grounded and in the SSA and TSSA this currentsource is coupled Direct to the emitter and modulated.
There Will only be a small benefit of changing it to a ccs. Biggest advantage would be a constant current source regardless of supply voltage.
Nothing more to say on this matter.
Yes, if they're capable as the ones from sch. Not so easy task these days.
Best replacement at the moment is 2n5401/2n5551. The have a relative low millercapacity. But they cannot handle more than 500mW.
Crt screen transistors are not used any more and the crt screen production where driving the manufactures.
What i mention has no impact on steady State values tinitus.
No AC drop on resistors means in any state, steady, signal present, whatever. No AC is no AC always, no modulation whatsoever if FB caps are good and rails ripple is zero.
Higher the rails DC, better percentage of current stability through 15k.
Merry Xmas! What is the PSRR figure as it is with the 15K source?
20*log 50uVmax/2V= -92db
how about this pair ?
http://www.ampslab.com/Freewares/2sa1145.pdf
http://www.ampslab.com/Freewares/2sc2705.pdf
UPS ! wattage might be ok, but looks like very low current
but I do have a few 2sa1930/2sc5171
not lowest output capacitance, but 16pf/26pf is midway, I guess
http://www.ampslab.com/Freewares/2sa1145.pdf
http://www.ampslab.com/Freewares/2sc2705.pdf
UPS ! wattage might be ok, but looks like very low current
but I do have a few 2sa1930/2sc5171
not lowest output capacitance, but 16pf/26pf is midway, I guess
They are just as hard to obtain. Sorry ... Best source for special parts are profusion.
http://www.ampslab.com/Freewares/2sb1109.pdf
http://www.ampslab.com/Freewares/2sd1609.pdf
yes, seems thats the way it goes
http://www.ampslab.com/Freewares/2sd1609.pdf
They are just as hard to obtain.
yes, seems thats the way it goes
20*log 50uVmax/2V= -92db
Where 50uV and 2V derive from?
- Home
- Vendor's Bazaar
- VSSA Lateral MosFet Amplifier