I need an extra-loud sound from a small piezo disc and thought
I'd give the inductor method a go. Usually a 1k resistor across the
piezo as a non-capacitive load for the transistor produces a loud
enough beep. This mail from a while back says how

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Wed, 16 Jun 2004 09:12:57, from Matt Pobursky

1. Find the capacitance of the piezo device, almost always listed in
the spec sheet.
2. Calculate the device's capacitive reactance at the frequency you will
be driving the device.
3. Calculate an inductor value for the equivalent inductive reactance.
4. Place an inductor of said value in parallel with the piezo device.
5. Drive the whole parallel piezo/inductor circuit with a FET/transistor
rated ~10x higher voltage than your voltage source.

======

My piezo, 27mm diaphragm, is around 15nF and resonates at 4.6kHz

Capacitive reactance Xc = 1/(2*pi f C), f = 4600, C = 15nF

Xc = 1/(6.28 * 4600 * 15*10^-9)
= 1/0.00043332
= 2308 ohms

Inductive reactance XL = 2*pi f L, XL = 2308, f = 4600, 2*pi = 6.28

L = XL/(2*pi f)
= 2308/(6.28 * 4600)
= 0.080H

80mH seems rather large. I was expecting perhaps a couple of
hundred uH (no evidence to presume that, apart from physical
size). Are my units and the method correct ?

TIA

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