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LM7171: Suggestion for an opamp part

Part Number: LM7171
Other Parts Discussed in Thread: OPA837, LM7705

HI,

I need suggestion for an OPAMP part with following specifications.

Offset voltage < 10uV

Slew rate > 800V/us

Gain bandwidth product > 90 MHz

Whether the offset voltage of higher slew rate opamps be lesser than 10uV.

  • What output swing do you need? Vpp or Vmin to Vmax. 

    Probably not going to find a part with those specs.

  • 2Vpk pk is required with the voltage high of 4V.

  • So a 2V to 4V swing, can you describe your input signal - I am thinking you have a some pulse waveform with a fast edge you are just trying to level shift.

    So a 2V transition requiring 800V/usec is a 2.5nsec kind of edge rate - sound right? Working backwards to a required SSBW, that is about 140MHz min SSBW. 

    10uV offset is kind of extremely tight for parts in that speed range. But, you probably don't need more than maybe a +/-6V part. or, with offset supplies, a -2 to +6V - kind of assuming non-RRO for this slew rate. 

    The OPA837 is close but as RRO you could get the swing voltages with a -0.23V on the negative supply using the LM7705 and then a +5V supply for the 4V output. But, the slew rate is not enough and the offsets (while many parts are actually in the +/-10uV window) is far wider. 

  • Hi Michael,

    Yes, my inout signal is 5Vpkpk square waveform at 5MHz frequency wherein i need a minimum steps of less than 10uV.

    My input is bipolar. I checked the opamp you have suggested (OPA837) which is a single supply opamp with 5V supply voltage.

    The requirement is high speed and slew rate of atleast 200V/us (considering my output as 1Vpkpk with 5ns edge rate).The critical part is to have lesser offset voltage probably less than 10uV(worst case).

    Thanks

    Pavithra Joshi

  • so you first say input is 5Vpp, then at the end you say the output is 1Vpp, attenuating by a factor of 5?

    So a 1Vpp output at 5nsec edge is not that big a deal asking for 200V/usec. The OPA837 could do this, but not the offset accuracy.