piezo booster

[harps]

hello

I wonder if anyone knows what type of IC and circuit would be good for boosting a piezo output by around x 1.5 ?

i have a 27mm piezo for triggering. but I need to boost it slightly before it goes into the computer, just slightly, so I have the range I need.

thanks for help.

[David Hess]

For maximum low frequency response, a low input bias current operational amplifier is often used.  If a higher low frequency cutoff is acceptable, then a high input bias current operational amplifier can be used.

Configure the operational amplifier in non-inverting mode, directly connect the piezo to the non-inverting input, and place a resistor across the piezo to sink the input bias current.

[harps]

Hello, thank you for your reply.

would a JFET be best, like an  OPA141 or OPA1641?

The resistor across the piezo to sink it,  what value would be a good starting point to try?

thank you for your help.

[David Hess]

Either the OPA141 or OPA1641 should work fine.  Note that low frequency noise is dominated by noise from the resistor so a low noise amplifier is not usually required.

Resistance values between 1 to 10 megohms are typical but can be higher in very low frequency applications.  The resistor only has to be low enough to sink the input bias current.  20 picoamps from either of the above amplifiers will yield only 20 microvolts of additional offset with a 1 megohm resistor.