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  • TI Thinks Resolved

THS4524: Gain setting resistor for THS4524

Part Number: THS4524

Hello

Whether I can use THS4524 as an attenuator of gain 0.5?

Gain setting resistor values comes to 47.5K and 100K with particular sensor I am using. Whether these values will cause any stability issues compare to data sheet values of 1K ? I have put 100pF capacitor across 47.5K.  I intend to use it in industrial environment.I have also put 100pf across 2 input terminals. 

  • Hi Sunil,

    Increasing the feedback and gain setting resistor values will have effect on stability due to external board parasitic. You may want to take a look at Section 8.3.8 in the THS4524 datasheet for this. However, inclusion of the 100pF feedback cap along with the input 100pF cap should help mitigate peaking in the frequency response or take care of this instability. I have attached a TINA-TI simulation result below that shows smooth roll-off of the ac response which indicates a stable circuit.

    Another way to approach your circuit would be to include a high impedance input, such as JFET or CMOS input, after the sensor to buffer the signal and then use the THS4524 for single-ended to differential conversion. A good device to buffer the sensor output signal is to use the OPA2810 which has JFET inputs.

    Best Regards,

    Rohit

    THS452x_G=0.5.TSC

  • In reply to Rohit Bhat:

    Thanks for the reply. Bandwidth of amplifier will be 10+ kHz with such high value of gain control resistors. In case of high frequency noise coupling, amplifier output will roll off resulting into drop in measurement values. Is there any other way to solve such problem other than using FET based opamp ?
  • In reply to Sunil Dwivedi98:

    Hi Sunil,

    Do you mean that you need higher frequency operation than 10kHz when you say high frequency noise coupling? If yes, then I believe it would make the problem solvable using FET based op-amp at the input in-order to buffer the signal, and then go from single-ended to differential signal using an FDA such as the THS4521 or THS4551.

    Best Regards,
    Rohit
  • In reply to Rohit Bhat:

    Hi Sunil,

    Please let us know if you need any help with the FET based op-amp input stage. A good part to choose would be the OPA2810 for this application.

    Best Regards,
    Rohit

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