Amplifier for piezoelectric sensor, OP Amp circuit

  • #1
hugo_faurand
61
10
Hello everyone !

I'm working with a piezoelectric cell and I need to retrieve the variation of the charge of the cell as a voltage signal.
I found this circuit (a charge amplifier) with an OP Amp ( here the piezo cell is represented as the current source with the capacitor and the resistor on the left).
I want to analyze the behaviour of the circuit and plot Bode diagrams for the V_out, but I'm not familiar with OP-amp.
I tried to do what I knew and starting with calculating the equivalent inductance of C_f and R_f but then I don't know how to go about with the current source and the Op-Amp.

techart_designCA_1.png




So if you can give me some clues to continue my work, please.

Thanks in advance.
 

Answers and Replies

  • #2
1,483
440
The output voltage ##V_\text{out}## is what ever it needs to be to make the voltage at the inverting input of the amplifier is equal to the non inverting input. One assumes the input impedance of the amplifier are infinite so there is no current flow into the inputs.
 
  • #4
berkeman
Mentor
64,179
15,398
Hello everyone !

I'm working with a piezoelectric cell and I need to retrieve the variation of the charge of the cell as a voltage signal.
I found this circuit (a charge amplifier) with an OP Amp ( here the piezo cell is represented as the current source with the capacitor and the resistor on the left).
I want to analyze the behaviour of the circuit and plot Bode diagrams for the V_out, but I'm not familiar with OP-amp.
I tried to do what I knew and starting with calculating the equivalent inductance of C_f and R_f but then I don't know how to go about with the current source and the Op-Amp.

View attachment 283027



So if you can give me some clues to continue my work, please.

Thanks in advance.
Can you say more about your background in EE? If you are not yet familiar with how to use opamps, are you familiar with discrete transistor amplifiers? What is your background with Bode plots? Do you understand the differences between HPF, LPF and BPF Bode plot responses? And how the number of poles and zeros affects those plots?

Can you say what the context of this project is? Is it lab work that you are doing at your job, or a school project of some sort? If for school, are you starting to learn about opamps in your class? If for a work project, it might be faster for you to use an amplifier instrument to interface with that piezo transducer.

Which piezo are you using/modeling? Can you link to the datasheet? What frequencies are the exciting forces, and is this an acoustic or mechanical pickup?

The 2nd opamp tutorial link posted above by @DaveE looks good, but it will take you a while to get up to speed. If you are learning about opamps in class as well, then that second link is a good reference to help you learn. If this is a project for work, I'd still go with the pre-built amplifier instrument instead to get you quicker results.
 
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  • #5
hugo_faurand
61
10
Can you say more about your background in EE? If you are not yet familiar with how to use opamps, are you familiar with discrete transistor amplifiers? What is your background with Bode plots? Do you understand the differences between HPF, LPF and BPF Bode plot responses? And how the number of poles and zeros affects those plots?

Can you say what the context of this project is? Is it lab work that you are doing at your job, or a school project of some sort? If for school, are you starting to learn about opamps in your class? If for a work project, it might be faster for you to use an amplifier instrument to interface with that piezo transducer.

Which piezo are you using/modeling? Can you link to the datasheet? What frequencies are the exciting forces, and is this an acoustic or mechanical pickup?

The 2nd opamp tutorial link posted above by @DaveE looks good, but it will take you a while to get up to speed. If you are learning about opamps in class as well, then that second link is a good reference to help you learn. If this is a project for work, I'd still go with the pre-built amplifier instrument instead to get you quicker results.
Thanks for your answer.

Actually, I only have little experience with opamp. I only know about classic circuit : inverter, derivator...

About Bode plot, it's the same. I' plotted Bode diagrams for basic op-amp circuit : Gain Diagram and Phase diagram.

Indeed, it's something like a school project. I'm working on ultrasound emitter/receptor (piezo) used in medicine. I want to find a circuit to simulate the behaviour of a such device and start to process the signal. In medicine, such devices provides an ultrasound signal with a frequency from 2MHz to 20 MHz.

Thanks in advance.
 
  • #6
Stonestreecty
20
3

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  • #7
dlgoff
Science Advisor
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