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Old 24th August 2010, 05:05 PM   #421
Baldin is offline Baldin  Denmark
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Quote:
Originally Posted by Eva View Post
..... These circuits won't achieve higher THD by oscillating at either higher or lower frequencies .....
You men lower, right? 240 kHz is the optimum ....
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Old 24th August 2010, 05:05 PM   #422
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Now im using IR2010 which have shorter delays than the IR2110 but atleast it would give a clue, just need to familiarize myself with ltspice, downloading the latest version atm.
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Old 24th August 2010, 05:19 PM   #423
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Crap! Theres no LM311 in ltspice
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Old 24th August 2010, 05:25 PM   #424
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Eva, what you write makes perfect sense ....
Make the circuit as fast as possible (propagation delay as little as possible), choosing fast comperators, fast level shifter, low propagaton driver and fast MosFets ... and choose an optimal switching freq. ....... but I'll have to do some more sims to determine what exactly the optimal freq is as I guess it changes with duty cycle (level out) ... at least the compromise betwen odd and even order harmonics ....

.... If not making UcD and therefore usnig an integrator in the input, what makes for the perfect opamp I wonder?
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Old 24th August 2010, 05:25 PM   #425
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Quote:
Originally Posted by Baldin View Post
You men lower, right? 240 kHz is the optimum ....
Yes, I meant lower THD
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Old 24th August 2010, 06:06 PM   #426
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Quote:
Originally Posted by Tekko View Post
Crap! Theres no LM311 in ltspice
Hello Tekko

Attached you can find the model

Regards,
savu
Attached Files
File Type: zip LM311.zip (968 Bytes, 435 views)
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Old 24th August 2010, 06:26 PM   #427
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Quote:
Originally Posted by Baldin View Post
Eva, what you write makes perfect sense ....
Make the circuit as fast as possible (propagation delay as little as possible), choosing fast comperators, fast level shifter, low propagaton driver and fast MosFets ... and choose an optimal switching freq. ....... but I'll have to do some more sims to determine what exactly the optimal freq is as I guess it changes with duty cycle (level out) ... at least the compromise betwen odd and even order harmonics ....

.... If not making UcD and therefore usnig an integrator in the input, what makes for the perfect opamp I wonder?
hello baldin,

A simple exercise of imagination.
You take a class d amp.

Input stage to output stage there are these components:

LT1711 - 4.5nS delay
HCPL-9000 - 12nS delay
TC4420 - 55nS delay (thinking of using very fast zetex transistors for better results)
IRFH5020 - 21nS delay

This is a total of 92.5nS propagation delay.
You will have a huge dv/dt.

Regards,
Savu
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Old 24th August 2010, 06:39 PM   #428
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So heres a sim of my prototype board:
Click the image to open in full size.
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Old 24th August 2010, 07:20 PM   #429
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Tekko: rast working

Savu .... not sure I get your point ... are you refering to my question on opamp choice?
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Old 24th August 2010, 07:43 PM   #430
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i am talking about a cladd d amplifier.
about the idea of making one that fast

regards,
savu
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