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LM358: Building a differential amplifier for a hall effect sensor

Markovicz
Prodigy 220 points
Part Number: LM358
Other Parts Discussed in Thread: TLV9001, TINA-TI, TLV6001

Dear e2e-Team,

I would like to amplify the signal of a honeywell hall effect sensor (model: SS59ET):

sensing.honeywell.com/.../ss39et-ss49e-ss59et

The sensitivity is around 1.5mV/G. The sensor output with no magnetic field is VCC/2. In my case, that would be 3.0V/2=1.5V since I would like to use a lithium coin cell for my project. Depending on the orientation of the magnet infront of the hall effect sensor, the output fluctuates in a range of +-5mV (in a distance of 2 cm) and +-15mV (in a distance of 1cm).

I am a beginner with opams and have built a basic differential amplifier using a LM358:

https://www.elektronik-kompendium.de/sites/slt/0210153.htm

Please see my circuit diagram below:

For the voltage divider I've used 2.2k, for the amplifier I used R1=2.2k and R2=22k & 68k. The results were quite promising but I'd like to ask the experts on how to design the amplifier better.

1. What resistor ratio do you recommend?

2. Size is essential for my project. Can you recommend smaller-sized opamps? For now, I am using only a single opamp and don't need an LM358.

3. Do you recommend any filter circuits?

Thank you!

  • 0
    TI__Expert 6625 points

    Hi Markovicz, 

    You're headed in the right direction. 

    Please take a look at this difference amplifier circuit: http://www.ti.com/lit/an/sboa274a/sboa274a.pdf. It is very similar to your current design with an additional Vref component. Please take a look, and let us know if you've any questions. 

    You do not need LM358 for this application since your supply voltage is much lower. I would recommend some low voltage rail-rail devices. Please find the comparison table below:

     

    If smaller package size is desired, I would recommend using TLV9001, it is available in X2SON package. 

    Next, I would highly recommend simulating your difference amplifier before design. You can use our free simulation software TINA-TI available at: http://www.ti.com/tool/TINA-TI. 

    Let us know if you've any other questions. 

    Regards,

    Bala Ravi

  • 0 in reply to Bala Ravi
    Prodigy 220 points

    Dear Bala,

    Thank you a lot for your help! I've already downloaded TINA and had some fun exploring the software and simulating some OPAMP circuit. My question has been more than resolved.

    I just have a little addon: is it possible to download components like the TLV9001 or the TLV6001 to support them in TINA?

    Thank you!

  • 0 in reply to Markovicz
    TI__Expert 6625 points

    Hi Markovicz, 

    That's great! Glad to hear that you're enjoying TINA-TI. 

    Yes, you can download the reference design for TLV9001 here: 

    Similarly, you can download the reference design for TLV6001 here: 

    I hope this helps!

    Regards,

    Bala Ravi

  • 0 in reply to Markovicz
    Guru 140200 points

    Hi Markowicz,

    you can download the TINA-TI reference designs directly from the product sites:

    Then, copy and paste the models from the TINA-TI reference design directly into your simulation. This guarantees (nearly always) that you get the latest model available.

    Kai