LT1167 Instrumentation Amplifier Gain

Discussion in 'General Electronics Chat' started by Dritech, Feb 15, 2016.

  1. Dritech

    Thread Starter Well-Known Member

    Sep 21, 2011
    Hi all,

    I am interested in using the LT1167 Instrumentation Amplifier (IA) to amplify a signal of few milliVolts. The datasheet states that the gain can be set with one external resistor to get gains of 1 to 10,000.
    In many instrumentation amplifiers applications I see of the internet, I notice that they apply small gain to the Instrumentation Amplifier and then use a secondary op-amp to apply the remaining gain, Is there a reason for doing so?
    I need a gain of 1000 but I am concerned that the higher the gain, the less the IA performance.

    From the datasheet of the LT1167 I noticed the following:

    Higher gain = higher nonlinearity
    Higher gain = longer settling time
    Higher gain = better CMRR
    Higher gain = less bandwidth

    Can someone please mention some advantages and disadvantages of increasing the IA gain?
    Shell I apply the full gain or use a secondary op-amp?

    Below is the link to the LT1167 datasheet:

    Thanks in advance,
  2. crutschow


    Mar 14, 2008
    Usually the reason for adding amplification at the output of the instrumentation amp is to improve the bandwidth for a given total gain.
    If you don't need the bandwidth then you shouldn't need an additional gain stage.
    Dritech likes this.
  3. ericgibbs

    Senior Member

    Jan 29, 2010
    hi Dri,
    I use a 2nd OPA which has a rail2rail output voltage range.
    The LT1167 has a output voltage limit of approx +/-1.2V less than the IA supply rails.
    So for a IA circuit powered by say +/-5V that would have a +/-3.8V limit.

    Also its possible to add extra noise filtering between the IA and the 2nd OPA.

    Dritech likes this.