please help me for getting ad 620 instrumentation amplifier output correctly.

Discussion in 'Homework Help' started by shibas, Feb 15, 2013.

  1. shibas

    Thread Starter New Member

    Feb 13, 2013
    Iam posting my circuit diagram of the Ad 620 instrumentation amplifier and the values of components used in the circuit in two separate attachments.please refer to it and mention any change if i have to make to the circuit to get the amplified output.When i connected this circuit first i was not getting the required gain.But now iam getting very huge gain than the gain that is required.The gain equation for ad 620 is G=(49.4k/rg)+1. isn't it? I need a gain of about 100 or below 100.please help me.I used the 0.1 uf capacitor between the input signal and the non inverting input to remove the dc offset components.Is that correct to use it?

    Do i need to insert a resistor between the inverting and non inverting input terminals of the op amp and ground that resistor to reduce the effect of the input bias current?
    Some body please help me.

    If the circuit diagram is wrong somebody please reply or upload a correct circuit diagram of the instrumentation amplifier using ad 620 ic.
  2. WBahn


    Mar 31, 2012

    Only put a given post in ONE forum. You already have this in at least four!

    Make up your mind.
  3. shibas

    Thread Starter New Member

    Feb 13, 2013
    Thank you to all.It finally worked well when i inserted a resistor of 1M ohm each(grounded) to both inverting and non inverting input terminal of the AD 620 ic.
    Also i removed the two capacitors c8 and c9 which was connected from the output to the ground.

    I designed the circuit for a gain of 105 using equation G=(49.4k/Rg)+1 using the Rg connected between pins 1 and 8 of the ic as 470ohm.
    But iam getting only a gain of about 100 or a gain value just below 100.

    Also in my output ac signal its negative half cycle amplitude is less than positive half cycle amplitude.What should i do to correct my output signal by making both half cycle amplitudes equal?

    What to do?some body please help.
  4. Ron H

    AAC Fanatic!

    Apr 14, 2005
    What is the tolerance of your 470Ω resistor? If the resistance is 5% high, your gain will nominally be 101, assuming the 49.4k is precisely that value.
  5. shibas

    Thread Starter New Member

    Feb 13, 2013
    My application is to amplify the signal output from a vibration sensor or vibration analyzer which is comparatively very less.For that will opamp ic 741 connected in non inverting configuration be suitable?

    some body please reply fast.