Subject: Re: Ultrasonic Transducers Amp - 15W 50kHz (20kHz bandwidth)
Date: Wed, 22 Jan 2003 04:03:35 +0000 (UTC)
NNTP-Posting-Date: Wed, 22 Jan 2003 04:03:35 +0000 (UTC)
User-Agent: tin/1.5.14-20020926 ("Soil") (UNIX) (Linux/2.4.20 (i686))
> Even though the 'power bandwidth' (this is a vague measure to start
> with) on home audio amps is rated up to 50kHz, I'd rather not try to
> run it at such a high frequency continuously.
> The input to the amp is from a signal generator, a 50kHz signal, say
> 1V at 100,000 ohms. The speakers (ultrasonic transducers) I'm driving
Probably 50 ohms, if it's a normal bench siggen.
> are at 700 ohms, but as long as the power is there from the amp, I can
> use transformers later to match impedance.
> Any suggestions for a (simple) design for an amp? What will the
> problems be at this high frequency regards components used?
You'r looking at around 155V p-p.
That's about right for a rectified 110V supply (isolation transformer!).
However, it's a bit high to be comfortable, and is certainly lethal if
you touch it.
What linearity are you looking for?
My personal first-cut at it, for a prototype would be to use a lower supply,
perhaps 15-0-15 or 12-0-12, as the voltages are safer, the components a little
You'r then looking at around an amp or so RMS, before the transformer.
I'd be tempted to go for a simple class B amplifier, made from a
couple of power transistors and either a beefy opamp, or a couple more
transistors driving them.
This could be around $5 or so in parts per channel, though you will need
heatsinking, and a 4 or 6 A power supply.
70Khz is not really that fast.
We could do with some more details.
What are you trying to do, how much distortion can you live with, and
what sort of speakers are you using?
http://inquisitor.i.am/ | mailto:firstname.lastname@example.org | Ian Stirling.
He had been eight years upon a project for extracting sunbeams out of cucumbers,
which were to be put in vials hermetically sealed, and let out to warm the air
in raw inclement summers. -- Jonathan Swift, "Gulliver's Travels" (1726)