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Qustion about opa2334

Ivan Petkov
Prodigy 20 points
Other Parts Discussed in Thread: OPA2334

Hello Everyone, I should design a DC amplifier with 2 two operational amplifiers, the gain that I should make is 2500, so I'm going to make it with 2 operational amplifiers 50*50
that sayed the proffesor, my input offset voltage should be less than 10mikroVolts so I choosed opa2334, but in the data sheet there's no information about input impedance (common and differencial mode), I need them to calculate Ria (of the amplifier which is Ria=Rid||Ricm), so how I can get the imput impedance of common and differencial mode.
One more question, in the output of my amplifier (the second one), I should get output voltage 3V, so is the output voltage swing from is the max. output voltage that the amplfier can work with at the output, or this is another thing :(
Can I get output voltage 3V with opa2334.... Sorry about my questions and English, I'm new here :)

  • 0
    Guru 21975 points

    Ivan,

    The input resistance of the OPA2334 can be inferred from the typical performance curve "Input Bias Current vs. Common-Mode Voltage" on page 4 of the data sheet. The input resistance is the inverse of the slope of these curves. As you can see, at moderate temperatures the resistance is extremely high, perhaps in the range of 1V/20pA, or 50G-ohms. This resistance is rarely a factor in circuit operation. The input bias current is generally the more important concern. This is shown on the same page.

    The OPA2334 can provide 3V output with a power supply greater than approximately 3.1V. The maximum operating voltage is 5.5V.

    Regards, Bruce.

  • 0 in reply to Bruce Trump
    Prodigy 20 points

    Thank you a lot, but now what about the differencial input resistance, how I can get it :? I need to both, to calculate Ria which is Ria=Rid||Ricm

  • 0 in reply to Ivan Petkov
    Guru 21975 points

    Ivan,

    Differential input resistance is in a similar range as common-mode resistance. Again, it is very rarely a factor in a properly operating amplifier circuit.

    Regards, Bruce.