On Wed, 25 Jun 2008 10:42:54 -0700 (PDT), use@[EMAIL PROTECTED]
wrote:
>
>> Right there in the text "The left side of the circuit uses a low-power
>> dual comparator (MAX9022) to form a relaxation oscillator..."
>>
>> So, (a) you've been _told_ what's going on, and (b) it's not an op-amp,
>> it's a comparator.
>
>OK, this is clear now, shame engineers use the same symbols for
>different things...
---
No, the shame lies with idiots like you, who have a do***ent in front
of them which clearly states that a _comparator_ is being used as a
relaxation oscillator and apparently don't even bother to read it.
---
>> On the right side of the circuit, consider what happens when a bunch of
>> AC shows up on the open end of C4.
>
>This is still not understood. The text talks about 155KHz, which is
>more
>than the human ear can hear, so which AC are we talking about?
>And even if we could hear 155KHz, D3 and C5 for a rectifier which
>converts any ac to dc, so how can a dc signal vibrate the piezo?
---
The 155kHz signal from the oscillator is being rectified and smoothed,
and then if the resultant DC rises to Vcc/2, the output of the second
comparator will go high and supply DC to the piezo buzzer, which has a
built in oscillator used to drive the piezo transducer.
And bottom post.
JF
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