• State
  • Locked Locked
  • Replies 1 reply
  • Subscribers 49 subscribers
  • Views 368 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

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.

opa2336

otto fest
Prodigy 10 points
Other Parts Discussed in Thread: OPA2336

I'm using OPA 2336(~4V single supply) w/unipolar positive signals few mW above ground successfully but need to use for ~100mV BIPOLAR inputs and have no space for dc-dc. I have used other single supplies w/limited(~100mV) bipolar input by adding a forward bias schottky(~200mV FVD) to the opamp ground. but the 2336 doesn't like it it saturates ~25mV above ground and I need to measure 0.000mv or negative signals

  • 0
    TI__Guru* 93105 points

    Hello Otto,

    I reviewed your circuit diagram that you sent to me privately. Single-supply operational amplifiers, even if described as being rail-to-rail output such as the OPA2336, don't quite swing to 0 V. The OPA2336 specifications indicate that it will swing to within 3 mV of 0 V, with a 100 k load. But certainly that is not 0 V and most amplifiers that do swing that close may actually be in saturation - no longer in operating in a linear mode (see the PowerPoint slides I have attached). That can add non-linearity to signals falling within that region of the output swing.

    My understanding is there are operational amplifiers that their output does swing to 0 V, and below. They have a built-in charge pump that places the internal -Vee rail to a negative voltage, realtive to 0 V. The OPA2336 does not have a negative rail charge pump.

    You describe adding a forward biased Schottky diode in series with the amplifier's negative supply pin. The diode, as you described, would raise the ground reference of the operational amplifier by a couple hundred millivolts. The amplifier's output stage would now be raised by that amount too. It would seem that would make even more difficult to swing close to 0 V. Maybe I am not visualizing the diode connection correctly. Could you provide a simplifier diagram showing how you connect the diode?

    Regards, Thomas

    PA - Linear Applications Engineering

     

    Op Amp Aol vs Vout.pptx