+ Post New Thread
Results 1 to 16 of 16
  1. #1
    e_e
    e_e is offline
    Newbie level 2
    Points: 1,129, Level: 7

    Join Date
    Sep 2006
    Posts
    2
    Helped
    0 / 0
    Points
    1,129
    Level
    7

    how to amplify voltage

    Hi,
    I need to know what type of op-amp configuration can be used to amplify the input voltage of mV to V ( a gain of 1000)

  2. #2
    Full Member level 6
    Points: 4,120, Level: 15

    Join Date
    Apr 2005
    Posts
    390
    Helped
    52 / 52
    Points
    4,120
    Level
    15

    mv to v amplifier

    Any real operational amplifier has two major problems:
    1. offset voltage
    2. thermal offset drift

    The offset voltage is found at the output of the amplifier, magnified with the gain
    when the input voltage is zero. Example: input zero mV, offset +3mV, gain 1000, configuration inverter. The output voltage will be -3x1000=-3000mV = -3V in the absence of any input voltage!

    The thermal offset drift is adding to the offset voltage. Example: 15uV/C will add 15uV to any celsius degree temperature modification, magnified also with gain. At 20C above ambiant temperature (meaning +40C) the output will be 15uV x 20 x 1000 = 300mV

    Conclusion: the output of an operational amplifier in inverting configuration may have 3000mV +/-300mV at 40C and ZERO input voltage.

    You must choose either a very low offset/low thermal drift OA and use AC magnification, or use two cascaded OA and either DC with offset compensation or AC magnification.



    •   Alt24th April 2007, 17:32

      advertising

        
       

  3. #3
    Full Member level 2
    Points: 3,081, Level: 13

    Join Date
    Dec 2001
    Posts
    126
    Helped
    9 / 9
    Points
    3,081
    Level
    13

    how to amplify mv to v

    Quote Originally Posted by e_e
    Hi,
    I need to know what type of op-amp configuration can be used to amplify the input voltage of mV to V ( a gain of 1000)
    With what precision (dynamic range), what bandwidth, what source impedance and what time scale of the measurement ?

    For example if input noise of say 100 nVrms/rtHz is acceptable and the signal bandwidth is within of kHz range, then some can use chopper stabilized (zero drift) OP, like for instance TLC2654, what insures good long time stability.



  4. #4
    e_e
    e_e is offline
    Newbie level 2
    Points: 1,129, Level: 7

    Join Date
    Sep 2006
    Posts
    2
    Helped
    0 / 0
    Points
    1,129
    Level
    7

    need to amplify voltage

    But the op-amp I studied, like single stage OTA, cascaded, folded cascode, they only have the gain in range of 10-100 right?
    So, how to get a such high gain of 1000?



    •   Alt25th April 2007, 02:23

      advertising

        
       

  5. #5
    Advanced Member level 1
    Points: 5,681, Level: 17

    Join Date
    Dec 2003
    Posts
    423
    Helped
    70 / 70
    Points
    5,681
    Level
    17

    amplify mv

    Quote Originally Posted by e_e
    But the op-amp I studied, like single stage OTA, cascaded, folded cascode, they only have the gain in range of 10-100 right?
    So, how to get a such high gain of 1000?
    folded cascode op has higher gain (>60dB) than simple OTA, and it's not difficult to build such a op, refered to Martin's book or Razavi's book.



  6. #6
    Member level 5
    Points: 2,209, Level: 10
    kokabanga's Avatar
    Join Date
    May 2005
    Posts
    88
    Helped
    13 / 13
    Points
    2,209
    Level
    10

    how to amplify 2 mv

    A simple inverting op-amp using the ua741 op-amp from National Semiconductor will do the trick.

    choose R2=1MOhm and R1=1KOhm



    •   Alt25th April 2007, 03:17

      advertising

        
       

  7. #7
    Full Member level 1
    Points: 2,057, Level: 10

    Join Date
    Nov 2006
    Posts
    99
    Helped
    5 / 5
    Points
    2,057
    Level
    10

    circuit to amplify 20 mv

    telescopic and folded cascode Ota will provide gain more than 60db(1000). but in telescopic the output range will be less.



  8. #8
    Full Member level 5
    Points: 4,350, Level: 15

    Join Date
    Mar 2004
    Posts
    282
    Helped
    15 / 15
    Points
    4,350
    Level
    15

    how to amplify mv

    Try folded cascode, telescopic or gain boosted cascode for gain maximization.



  9. #9
    Newbie level 1
    Points: 1,012, Level: 7

    Join Date
    Apr 2007
    Posts
    1
    Helped
    0 / 0
    Points
    1,012
    Level
    7

    amplify voltage from mv

    You may try differential opamp AMP04.



  10. #10
    Member level 1
    Points: 1,767, Level: 9
    Achievements:
    7 years registered
    rush3k's Avatar
    Join Date
    Mar 2006
    Posts
    38
    Helped
    8 / 8
    Points
    1,767
    Level
    9

    thermal offset opamp

    Quote Originally Posted by e_e
    But the op-amp I studied, like single stage OTA, cascaded, folded cascode, they only have the gain in range of 10-100 right?
    So, how to get a such high gain of 1000?
    With a two-stage OTA, you can get more than 1000 v/v gain.



  11. #11
    Junior Member level 1
    Points: 1,288, Level: 8

    Join Date
    Mar 2006
    Posts
    17
    Helped
    1 / 1
    Points
    1,288
    Level
    8

    Re: how to amplify voltage in range mV to V

    use instrument amplifier u can vary the gain in instrument amplifier. it is mainly for this purpose. Some companies like AD(analog devices),TI(texas instruments are offering this instrument amplifier ic packages.



  12. #12
    Newbie level 2
    Points: 1,217, Level: 7

    Join Date
    Feb 2007
    Posts
    2
    Helped
    1 / 1
    Points
    1,217
    Level
    7

    Re: how to amplify voltage in range mV to V

    easily with opamp


    1 members found this post helpful.

  13. #13
    Member level 5
    Points: 1,867, Level: 10

    Join Date
    May 2006
    Posts
    86
    Helped
    3 / 3
    Points
    1,867
    Level
    10

    how to amplify voltage in range mV to V

    simple two stages CMOS opamp may esaily supplymore than 80dB(10000) in 0.6 process. one stage normally 40dB, folded cascode normally 60dB.

    SO , it is depend on what process you use and other characteristics you want.



  14. #14
    Junior Member level 2
    Points: 1,239, Level: 7

    Join Date
    Apr 2007
    Posts
    23
    Helped
    0 / 0
    Points
    1,239
    Level
    7

    how to amplify voltage in range mV to V

    use the swithed capacitor amplifier for the accurate amplification



  15. #15
    Junior Member level 2
    Points: 1,531, Level: 8

    Join Date
    Jul 2006
    Posts
    21
    Helped
    0 / 0
    Points
    1,531
    Level
    8

    how to amplify voltage in range mV to V

    @_@



  16. #16
    Member level 3
    Points: 1,182, Level: 7

    Join Date
    Jul 2008
    Posts
    57
    Helped
    8 / 8
    Points
    1,182
    Level
    7

    how to amplify voltage in range mV to V

    maybe you need a two or three stage opamp or use gain boosting to boost your open loop gain >> 60dB.

    Also determine how accurate you want your gain to be.
    60dB of gain +-1% requires an open loop gain of 100dB. So if your signal bandwidth is 1kHz you would need an 100MHz opamp with an open loop gain >100dB to obtain a +-1% 60dB over 1kHz. That's hard for an opamp.

    60dB of open loop gain in a 60dB gain setting would lead to 54dB closed loop gain.



+ Post New Thread
Please login