• State
  • Locked Locked
  • Replies 1 reply
  • Subscribers 47 subscribers
  • Views 2108 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

LMP7721: Components for AN-1798 potentiostat

Max Grell
Prodigy 10 points
Part Number: LMP7721
Other Parts Discussed in Thread: LMP91000

I am building NFC powered sensors, I am looking for some guidance relating to AN-1798 potentiostatic circuit provided by TI  http://www.ti.com/lit/an/snoa514c/snoa514c.pdf and finding the best components (op amps, JFETS).

I am seeking an op-amp with:

(1) Maximum 1.8V and μA input

(2) High power supply rejection ratio (because we are using NFC and our supply is fluctuating from 2.4V - 2.6V)

(3) Instrumentational op-amp

(4) Low input bias current, because we need precision

I would be grateful for any suggestions.

Also suggestions for a p-type JFET.

Thanks!

  • 0
    TI__Mastermind 32395 points

    Hello Max,

     

    We have the LMP91000 IC that is made for this application and could be an easy alternative, but I need more information to offer more recommendations with discrete op amps.

    1. For your requirement (1), are you saying the amplifier needs to be able to accept input signals up to 1.8V and 1uA? If so, do you mean the amplifier’s Absolute Maximum Voltage Input specification or its Input Common Mode needs to satisfy the 1.8V maximum input?

    2. What sensor or type of sensor are you using?

    3. Are you supplying a single supply of 2.5V to your amplifiers and what component is regulating voltage?

    4. For your requirement (3), why do you specify needing an instrumentation amplifier? I cannot see a way that using INAs will provide a benefit over standard operational amplifiers in the considered circuit below:

    Overall, INAs have very high input impedance and pre-set internal feedback resistors so you won’t be able to control the gain if you use them as a trans-impedance amplifier.

     

    Peter Iliya

    Precision Amplifiers

    Tucson, Arizona