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Old 31st August 2007, 08:17 AM   #1
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Post 100k freqency responce

I got a very difficult problem, as I want to design a power amplifier to drive my ultrasonic load, about 80w, I have to get the frequency responce to be as high as 100K. the frequency responce below 20k is not very important.
But all the audio power amplifier chips give the frequency resp only between 20-20k, so I can not figure out which one can be used.
Is there anyone who know which chip or modulation can fit my request.
If I buy a Ucd 180, change the input filter, can I get those request all fitted?
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Old 31st August 2007, 12:40 PM   #2
fumac is offline fumac  China
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100k respontŁ¬
show u my MCD respone

10hz~100khz +-0.xdb
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Old 31st August 2007, 12:43 PM   #3
fumac is offline fumac  China
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up to 140k-2db
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Old 31st August 2007, 12:52 PM   #4
BWRX is offline BWRX  United States
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Default Re: 100k freqency responce

Quote:
Originally posted by kz0071985
If I buy a Ucd 180, change the input filter, can I get those request all fitted?
If there is a low pass filter on the input you will need to change that, but more importantly, you will need to change the output filter. How accurate does this amp have to be at ultrasonic frequencies?
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Old 31st August 2007, 12:52 PM   #5
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As a rule of thumb, the PWM frequency needs to be 10 times the system bandwidth. So will will need around 1 MHz and just changing the input filter will not do the job.
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Old 31st August 2007, 12:59 PM   #6
fumac is offline fumac  China
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Quote:
Originally posted by sawreyrw
As a rule of thumb, the PWM frequency needs to be 10 times the system bandwidth. So will will need around 1 MHz and just changing the input filter will not do the job.
yes
my MCD is running at 1mhz(900k~1.2M 500w version )
a picture , this is the idel output 10hz~1mhz
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Old 31st August 2007, 11:03 PM   #7
maw1 is offline maw1  United States
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Why not use a simple linear amplifier and burn 40 watts of heat in the pass transistors? Cheap and easy solution.

Cheers, Mark
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Old 1st September 2007, 12:25 AM   #8
OzMikeH is offline OzMikeH  Australia
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Many off the shelf domestic amplifiers will do 100kHz. I have a cheap name brand second hand AV receiver that does it (allegedly).

Has this thread been started in Class D for efficiency reasons?
What is the ultrasonic load, an echo sounder type device?

PI metal detectors work by kicking a tuned circuit with a high voltage pulse, let it ring for a few cycles then ground out the oscillation just before "listening"
A similar concept might work for your application.
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Old 1st September 2007, 04:11 AM   #9
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OzMikeH, you got my point, the reason why I start the thread here is the high effiency the class D can achieve, I already figure out a linear amplifier, but the effiency is very low, and I have to give it a very big radiator, so I want find a new solution to solve this problem.
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Old 2nd September 2007, 05:26 AM   #10
fumac is offline fumac  China
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if u just for a 55k or 80k sqeare signal
u can build a switch amp (not class-d amp)

also high effect,

best rg
fumac
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