OMG! I am extremely sorry to hear this. Been away for sometime. He was a great designer that too being a dental surgeon - DDS. He addressed me as 'dear colleague', me being a cardiologist. He had a masters in electronics too. What a man with dual interest in medicine and electronics. He excelled in both. RIP Dr.Bora. Your designs will last long and bring happiness to many.
Welcome
I would like to open some projects by Dr. Bora, among others FlatBT.
I have already built a live prototype, but on the original as far as the transistors in the entrance as well as Vas( BC550/BC560 instead of 2sa872/2sc1775).
I have oscillations at the output 5.31MHz, adding small capacitors to the base / collector almost does not change anything. So I turned on the simulations, which also shows oscillations, and it's hard for me to do something about it myself.
I will try to place pictures, and simulations.
I would like to open some projects by Dr. Bora, among others FlatBT.
I have already built a live prototype, but on the original as far as the transistors in the entrance as well as Vas( BC550/BC560 instead of 2sa872/2sc1775).
I have oscillations at the output 5.31MHz, adding small capacitors to the base / collector almost does not change anything. So I turned on the simulations, which also shows oscillations, and it's hard for me to do something about it myself.
I will try to place pictures, and simulations.
Attachments
Last edited:
On your LTSPICE schematic, Q15 has collector/emitter swapped.
For stability I found the circuit is stable with C6 = 33pF, a 10pF capacitor across R17, and a 10R/100nF Zobel on the output. However, I dont like the look of the phase/gain margin and would tweak it further...
For stability I found the circuit is stable with C6 = 33pF, a 10pF capacitor across R17, and a 10R/100nF Zobel on the output. However, I dont like the look of the phase/gain margin and would tweak it further...
Attachments
Last edited:
Member
Joined 2009
Paid Member
This design was made by boromega more than a decade ago, it appears in post 94. I asked boraomega to explain this circuit sometime around 2015, but he declined, said it was not public. I don’t suppose it should still be considered secret and I’m still curious what are the engineering ideas behind this compound amplifier if anybody is able to explain ?..
Attachments
Hi Gareth,
This is a variant of ODNF (Only Distortion Negative Feedback).
The idea is that he subtracts the input signal from the output signal, resulting in the error signal, normalizes its amplitude (U2), and then subtracts the error signal from the total (input + error) signal (U1), reducing the distortion.
I also used this kind of approach in my Simpelstark amplifier, however, I've got U1 as a highly linear no-global-feedback non-inverting amplifier, subtracting the error signal at the output of trans-impedance (VAS) stage.
In any case, you can consider ODNF as a special way of implementing the global negative feedback, although it allows some cool features, comparing to the "classic" feedback approaches.
At least one Japanese manufacturer - Luxman - uses ODNF in its top amplifiers product line.
Cheers,
Valery
P.S. A few links to my implementation of ODNF:
"The way it works" explanation
Simpelstark V1.1 schematic
