TLV2771: App. note SLOA033A - signal conditioning piezoelectric sensors

Miheer Mayekar

Part Number: TLV2771

Can some one please give me detailed derivation of higher cutoff and lower cutoff frequencies of charge mode and voltage mode amplifier given in application note sloa033a?

I have simulated both the circuits given in this app. note and my calculated values of cutoff frequencies are not matching with the simulated values. I have derived them by my own and want to cross check them.

over 7 years ago

0 Ron Michallick over 7 years ago

TI__Guru*** 140026 points

Miheer,

The formulas used are the standard cut off frequency formula Fc = 1 / ( 2 * pi * R * C)
This is the frequency where resistance R is same magnitude as reactance Xc = 1 / (2 * pi * C * F)

Do you have a TI-Tina circuit to share?

0 Miheer Mayekar over 7 years ago in reply to Ron Michallick

Prodigy 70 points

Thank you very much Ron for your reply. I am attaching the TINA TI files for your reference. Current mode simulated results are not at all matching with the calculated values. Voltage mode simulated results are somewhat matching with the calculated values.current mode amp.TSC vtg mode amp.TSC

0 Ron Michallick over 7 years ago in reply to Miheer Mayekar

TI__Guru*** 140026 points

Miheer,

I looked closer at the section 3.2 Charge mode amplifier and the description doesn't look correct to me.

From the value you chose, I believe the lower cutoff should be 800 Hz and the upper cutoff should be 3200 Hz.

I made modification to your circuit to get the cut off values.

The lower cutoff is based on C4, R4 and upper is R1 and C2

current mode amp (1).TSC

0 Miheer Mayekar over 7 years ago in reply to Ron Michallick

Prodigy 70 points

Thanks Ron for your efforts. I'll get back to you regarding this issue soon.

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TLV2771: App. note SLOA033A - signal conditioning piezoelectric sensors