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Old 15th May 2018, 12:04 PM   #11
kokoriantz is offline kokoriantz  Lebanon
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This amp is dc coupled. The capacitors are the reservoir electrolytic capacitors of the power supply . You can replace in the circuit by batteries if you prefer .

Warning with DN2540N5 . As mosfet it is sensitive to electrostatic. Before soldering short the pins with an aluminum foil or wire at the base . Just touching the gate with non isolated soldering iron the gate channel junction got leakage.
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Old 16th May 2018, 12:34 PM   #12
padamiecki is offline padamiecki  Poland
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Quote:
Originally Posted by alexberg View Post
It's a push-pull gain stage with I-V conversion in signal path, capacitive coupling and floating PSU.
What's the purpose? Making simple things hard to make.
the amp is fine, I like it very much!
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Old 16th May 2018, 09:20 PM   #13
Ketje is offline Ketje  Belgium
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If you organise the drawing more classical one sees that it is an amp with a Schade-like feedback and a CCS to set the bias current.
Mona
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Old 17th May 2018, 11:46 AM   #14
Ketje is offline Ketje  Belgium
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My first drawing was with the 1k resistor on the wrong place.After correcting it i forgot to change the currents accordingly
Here are the right ones (i hope )
Mona
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Old 17th May 2018, 11:57 AM   #15
padamiecki is offline padamiecki  Poland
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Thanks Ketje, I even like it much now ;-)
what is the deep of nfb with this 1k res?
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Last edited by padamiecki; 17th May 2018 at 12:02 PM.
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Old 19th May 2018, 07:57 AM   #16
kokoriantz is offline kokoriantz  Lebanon
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Default The output circuit explained

This output circuit is described in details along other complimentary ones in any electronic textbook in the future . Consider first just a pair of complimentary mosfets biased at 1.3A and 8 ohms load. Each mosfet has a trans conductance of 1 A/V , if 1 volt is applied on the gates by a voltage source it develops 16 volts on 8 ohms load , voltage gain=16 .

The transistors has a total input capacitance of 2.3nF ,made of 1.5nF gate-source and total reverse 50pF x (gain+1) . The load sees the ouput as high impedance of 750pF . Loudspeakers are designed to function with low impedance outputs which should not exceed one tenth of the speaker's cooper resistance . Nowadays they are as low as 5 ohms . By adding a reverse resistor of 1khoms and driving the amp by a high impedance current source , every volt that the speaker utters is heard 5/5 by the gates which in turn answers with a current in reason of 2A/V , the speaker now sees the output as 0.5ohms . As the frequency goes higher the input capacitance of 2.3nF deafens the gates and above 70khz the output impedance becomes inductive of 1.13uH . This is unique among amplifiers to have a single pole with asymptote phase shift of 90°. It will require a parasite capacitor of 4uf to provoke an overshoot of Q=1 on square wave. Such robust output does not need any Zobels .

If 1volt of output from this amp is demanded, it must provide a current of 1/8 A and about 1ma for the reverse resistor , gates voltage is to become 62.5mv, after which ,the voltage across the 1kohms reverse resistance to be 1.0625V . The input current source has to inject 1.0625ma to have 1V output ,this gives a trans resistance of 941ohms or 0.941A/ma . The input current source now sees the input impedance as 62.5 ohms shunted by 2.3nF input capacitance which results a frequency responce of 1.15Mhz always of single pole 6db/octave instead of 2 as in other amplifiers .As it doesn't have slew rate limitation, the power bandwith is also 1.15Mhz.

At 1W it has 0.002%Td (sim). This unique transfer function alied with the output impedance, is the reason for the exceptional voice of this amplifier . If BJT transistors having beta of 100 were used ,it would required 100ohms reverse resistance , with 10 times more driving current. This amp can perfectly function in class AB with bias current of 150ma , but the trans conductance of the mosfets becomes 0.5 each, resulting output impedance of 1 ohms suitable for 16 ohms load but 60 watts power ,0.02%Td at 1W ,500khz fr with 2.2kohms reverse resistor . Just adding 6db NFR to accommodate 8 ohms load, and the charming voice evaporates.

Kokoriantz

Katje,thank you for your help.
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Old 19th May 2018, 03:27 PM   #17
alexberg is offline alexberg
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Quote:
Originally Posted by kokoriantz View Post
This amp is dc coupled. The capacitors are the reservoir electrolytic capacitors of the power supply . You can replace in the circuit by batteries if you prefer .
...
You have very peculiar way of drawing and explaining things... very strange full wave rectifiers. Not sure if double diodes are needed for decoupling (prevention of circulating currents) etc. Still floating PSU is no good regardless to whatever claims you have, it can't produce decent S/N due to capacitive coupling between floating sources.
As others mentioned it's a CFB kin so what makes if "new" per say?
Is there a specific purpose of claiming it new?
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Old 19th May 2018, 03:47 PM   #18
Pascal Nguyen is offline Pascal Nguyen  Australia
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Default Main wheel

Quote:
Originally Posted by MossFed View Post
Thanks for sharing this information.
I haven’t build the whole bicycle yet, just a mono wheel ...
The whole bicycle is running (without 1 k resistor) on Aarta.

Go to bed now, will put a 1k in and going to build a transformer with copper shield for the 9V coil by tomorrow.
Cheers and
Thanks again Mr K
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Old 21st May 2018, 12:21 AM   #19
Pascal Nguyen is offline Pascal Nguyen  Australia
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Default 9V coil ES shield

Well, it had to be done twice.
First attempt failed due to overlap foil shorted, unwound 100 turns.
Second attempt with much more thicker tape insulation, rewound 100 turns, job done.
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Old 21st May 2018, 12:37 AM   #20
Pascal Nguyen is offline Pascal Nguyen  Australia
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Default C3 - C4 2.2m not enough!

First disappointment , on floating rectified 9V supply, without 1k R feedback, my bicycle is oscillating.
Second disappointment, 50Hz is -40dB at the output, it was reduced to -60dB with C-R add on (10mF and 2.7R)
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