+ Post New Thread
Page 1 of 4 1 2 3 ... LastLast
Results 1 to 20 of 69
  1. #1
    Full Member level 1
    Points: 522, Level: 4

    Join Date
    Feb 2020
    Posts
    117
    Helped
    0 / 0
    Points
    522
    Level
    4

    how to boost microvolts to higher voltages?

    if i want to build a circuit that will boost 10 microvolts into say 10 millivolts, should
    i use an inverting amplifier or noninverting amplifier?

  2. #2
    Super Moderator
    Points: 83,919, Level: 70
    Achievements:
    7 years registered
    Awards:
    2nd Helpful Member
    betwixt's Avatar
    Join Date
    Jul 2009
    Location
    Aberdyfi, West Wales, UK
    Posts
    13,811
    Helped
    4581 / 4581
    Points
    83,919
    Level
    70

    Re: how to boost microvolts to higher voltages?

    That depends entirely on whether you want an exact but bigger voltage or one inverted in polarity. The amplification is the same regardless.

    Brian.
    PLEASE - no friends requests or private emails, I simply don't have time to reply to them all.
    It's better to share your questions and answers on Edaboard so we can all benefit from each others experiences.



    •   AltAdvertisement

        
       

  3. #3
    Advanced Member level 5
    Points: 10,193, Level: 24
    d123's Avatar
    Join Date
    Jun 2015
    Posts
    1,783
    Helped
    410 / 410
    Points
    10,193
    Level
    24

    Re: how to boost microvolts to higher voltages?

    Hi,

    You would need to provide more information and if possible any schematic related to yor actual circuit/design.

    Asking inverting or non-inverting sounds like a 'trick' question where the obvious non-inverting OA will turn out to be a useless answer because all important facts/data were not provided....



  4. #4
    Advanced Member level 5
    Points: 15,453, Level: 30
    schmitt trigger's Avatar
    Join Date
    Apr 2013
    Posts
    2,572
    Helped
    822 / 822
    Points
    15,453
    Level
    30

    Re: how to boost microvolts to higher voltages?

    To boost a signal with those ultra-low input levels, a high common-mode rejection will be required most certainly.

    That suggests a full-differential amplifier.
    My batteries are recharged by "Helpful Post" ratings.
    If you feel that I've helped you, please indicate it as a Helpful Post



  5. #5
    Advanced Member level 5
    Points: 13,290, Level: 27

    Join Date
    Aug 2015
    Location
    Melbourne
    Posts
    2,180
    Helped
    797 / 797
    Points
    13,290
    Level
    27

    Re: how to boost microvolts to higher voltages?

    are you talking amplifying a signal using a separate power source - or - do you only have uV and want to convert it to mV ... ?



  6. #6
    Super Moderator
    Points: 81,905, Level: 69
    Achievements:
    7 years registered
    Awards:
    Most Frequent Poster 3rd Helpful Member

    Join Date
    Apr 2014
    Posts
    16,627
    Helped
    3764 / 3764
    Points
    81,905
    Level
    69

    Re: how to boost microvolts to higher voltages?

    Hi,

    It depends on:
    Source impedance, currents, frequency response, noise, expected accuracy, supply voltage(es)...

    Guessing:
    If it's for amplifying a measurement signal, then I call for a chopper stabilized Opamp.

    Klaus
    Please don´t contact me via PM, because there is no time to respond to them. No friend requests. Thank you.



  7. #7
    Full Member level 1
    Points: 522, Level: 4

    Join Date
    Feb 2020
    Posts
    117
    Helped
    0 / 0
    Points
    522
    Level
    4

    Re: how to boost microvolts to higher voltages?

    i am using a NJM4558 dual operational amplifier, it is in an inverting configuration. it is receiving power from a 1.5 volt battery. i have also tried using a 4 volt 18650 lithium ion battery. if i connect the inverting amplifier to the 1.5 volt battery and there is no signal, the output is 0.856 volt. if i connect the inverting amplifier to the 4 volt 18650 lithium ion battery and there is no signal, the output is 3.26 volts. however if i connect the inverting amplifier to a voltage divider, which is suppose to be providing the signal, the output does not increase or decrease. the signal is 400 microvolts. if i use a much larger voltage, the output increases by 1 volt. i don't remember the value. i am trying to build a circuit that will increase 10 microvolts to 10 millivolts. i tried adjusting the ratio of feedback resistor to input resistor.

    Click image for larger version. 

Name:	Drawing(1).jpeg 
Views:	15 
Size:	56.2 KB 
ID:	157725

    this is a schematic of the circuit i am using.



  8. #8
    Super Moderator
    Points: 81,905, Level: 69
    Achievements:
    7 years registered
    Awards:
    Most Frequent Poster 3rd Helpful Member

    Join Date
    Apr 2014
    Posts
    16,627
    Helped
    3764 / 3764
    Points
    81,905
    Level
    69

    Re: how to boost microvolts to higher voltages?

    Hi,

    You need to read and understand datasheets.
    The NJM Opamp is completely unsuitable for this application in several ways.
    * it needs at least +/-4V = 8V to operate properly
    * it's offset voltage is higher than your expected input signal.(it's like you want to exactly measure temperature of 0...4° with a thermometer with an uncertainty of 5°)

    And you need to learn about the input voltage range of an Opamp circuit.
    Your schematic isn't clear where your input signal is referenced to.

    Klaus
    Please don´t contact me via PM, because there is no time to respond to them. No friend requests. Thank you.



    •   AltAdvertisement

        
       

  9. #9
    Super Moderator
    Points: 265,324, Level: 100
    Awards:
    1st Helpful Member

    Join Date
    Jan 2008
    Location
    Bochum, Germany
    Posts
    46,357
    Helped
    14108 / 14108
    Points
    265,324
    Level
    100

    Re: how to boost microvolts to higher voltages?

    Some key specs missing: Signal bandwidth, source impedance, acceptable noise level (specified as voltage density or wideband noise level, e.g. 0.1 to 10 Hz µVpp), acceptable offset voltage (if DC capable amplifier is intended) and drift.

    For sub µV offset, a "zero drift" (chopper stabilized) amplifier is probably required. TI has several zero drift OPs with < 2V supply voltage.



  10. #10
    Full Member level 1
    Points: 522, Level: 4

    Join Date
    Feb 2020
    Posts
    117
    Helped
    0 / 0
    Points
    522
    Level
    4

    Re: how to boost microvolts to higher voltages?

    Quote Originally Posted by KlausST View Post
    Hi,

    You need to read and understand datasheets.
    The NJM Opamp is completely unsuitable for this application in several ways.
    * it needs at least +/-4V = 8V to operate properly
    * it's offset voltage is higher than your expected input signal.(it's like you want to exactly measure temperature of 0...4° with a thermometer with an uncertainty of 5°)

    And you need to learn about the input voltage range of an Opamp circuit.
    Your schematic isn't clear where your input signal is referenced to.

    Klaus
    so what operational amplifier should i use for this application? is the lm224 operational amplifier suitable for this application?



    •   AltAdvertisement

        
       

  11. #11
    Super Moderator
    Points: 83,919, Level: 70
    Achievements:
    7 years registered
    Awards:
    2nd Helpful Member
    betwixt's Avatar
    Join Date
    Jul 2009
    Location
    Aberdyfi, West Wales, UK
    Posts
    13,811
    Helped
    4581 / 4581
    Points
    83,919
    Level
    70

    Re: how to boost microvolts to higher voltages?

    The LM224 can run off 4V but the highest voltage it can output is Vs-1.5.

    The information you need is in data sheets, you should be particularly interested in:
    Being able to work from a low supply voltage,
    Large enough output voltage swing,
    Low noise (or your microvolt signal will be lost in it)
    Low drift.

    Most manufacturers web pages have parametric search systems, if you put your requirements in it lists suggested devices that fit your needs.

    Brian.
    PLEASE - no friends requests or private emails, I simply don't have time to reply to them all.
    It's better to share your questions and answers on Edaboard so we can all benefit from each others experiences.



  12. #12
    Super Moderator
    Points: 265,324, Level: 100
    Awards:
    1st Helpful Member

    Join Date
    Jan 2008
    Location
    Bochum, Germany
    Posts
    46,357
    Helped
    14108 / 14108
    Points
    265,324
    Level
    100

    Re: how to boost microvolts to higher voltages?

    is the lm224 operational amplifier suitable for this application?
    Having already multi mV range offset: surely not.



  13. #13
    Full Member level 1
    Points: 522, Level: 4

    Join Date
    Feb 2020
    Posts
    117
    Helped
    0 / 0
    Points
    522
    Level
    4

    Re: how to boost microvolts to higher voltages?

    i tried building an inverting amplifier. i connected the inverting amplifier to 7.99 volt battery. the signal it receives is 1.45 volts.
    the input resistor has a resistance of 1000 ohms. i tried changing the resistance of the feedback resistor to 1000 ohms, 2000 ohms, 3000 ohms, 22000 ohms, i kept getting the same output 1.45 volts.
    why am i not getting different output each time i change the resistance of the feedback resistor?
    Click image for larger version. 

Name:	30d92f5f-ff5b-4978-b1ab-ae024717afdf.jpeg 
Views:	9 
Size:	58.0 KB 
ID:	157730



  14. #14
    Advanced Member level 2
    Points: 3,126, Level: 13

    Join Date
    Jan 2019
    Posts
    572
    Helped
    149 / 149
    Points
    3,126
    Level
    13

    Re: how to boost microvolts to higher voltages?

    as i read your sketch, the power supply to the op amp is one battery.
    the batteries are in anti-series, with the top battery connected to the two power inputs to the op amp

    the batteries should be in series with the top of the "upper" battery going to the upper power input of the op amp
    and the bottom of the "bottom" battery connected to the bottom power input to the op amp

    the voltmeter is connected to the output
    what is the voltage at the input and at the output?

    when you say there is no signal, is the input open, or tied to ground?
    if its open, there's no telling where the input will float to.



  15. #15
    Full Member level 1
    Points: 522, Level: 4

    Join Date
    Feb 2020
    Posts
    117
    Helped
    0 / 0
    Points
    522
    Level
    4

    Re: how to boost microvolts to higher voltages?

    The input is 1.45 volt. Output is always 1.45 volts. I tried changing the resistance of the feedback resistor, but I won't get different outputs. The 1.45 volt battery is suppose to provide the input. Why don't I get different outputs when I change the resistance of feedback resistor?



  16. #16
    Super Moderator
    Points: 81,905, Level: 69
    Achievements:
    7 years registered
    Awards:
    Most Frequent Poster 3rd Helpful Member

    Join Date
    Apr 2014
    Posts
    16,627
    Helped
    3764 / 3764
    Points
    81,905
    Level
    69

    Re: how to boost microvolts to higher voltages?

    Hi,

    The power supply battery has no other connection than the Opamp's supply.
    Thus all the other circuitry is floating w.r.t the supply. This can't work.
    --> You need some connection between power supply and input signals.

    What Opamp did you use?

    Klaus
    Please don´t contact me via PM, because there is no time to respond to them. No friend requests. Thank you.



  17. #17
    Full Member level 1
    Points: 522, Level: 4

    Join Date
    Feb 2020
    Posts
    117
    Helped
    0 / 0
    Points
    522
    Level
    4

    Re: how to boost microvolts to higher voltages?

    I used a njm4558 OP amp.



    •   AltAdvertisement

        
       

  18. #18
    Advanced Member level 2
    Points: 3,126, Level: 13

    Join Date
    Jan 2019
    Posts
    572
    Helped
    149 / 149
    Points
    3,126
    Level
    13

    Re: how to boost microvolts to higher voltages?

    i see you put up a new sketch.
    please re-post with resistor values written next to the resistors and
    please put the pin numbers of the op-amp on the sketch.



  19. #19
    Full Member level 1
    Points: 522, Level: 4

    Join Date
    Feb 2020
    Posts
    117
    Helped
    0 / 0
    Points
    522
    Level
    4

    Re: how to boost microvolts to higher voltages?

    i tried a different circuit.
    Click image for larger version. 

Name:	c1eec1f0-c817-424e-8432-eeea3b8f50d6.jpeg 
Views:	9 
Size:	74.2 KB 
ID:	157736

    this is a schematic of the new circuit. will this one work.the 1.45 volt battery's negative terminal which is suppose to provide the input, the 7.79 volt battery, which is the power supply battery, and operational amplifier's noninverting terminal are connected to the breadboard's negative rail. i tried using resistors with different values

    feedback resistor input resistor output
    459 ohm 44000 ohm 7.07 volt
    459 ohm 22000 ohm 7.03 volt
    1000 ohm 22000 ohm 7.03 volt
    1000 ohm 1000 ohm 6.54 volt
    2000 ohm 1000 ohm 6.54 volt
    3000 ohm 1000 ohm 6.58 volt
    22000 ohm 1000 ohm 7.03 volt
    44000 ohm 459 ohm 7.07 volt

    these are the values i got. is this noninverting amplifier working?



  20. #20
    Super Moderator
    Points: 81,905, Level: 69
    Achievements:
    7 years registered
    Awards:
    Most Frequent Poster 3rd Helpful Member

    Join Date
    Apr 2014
    Posts
    16,627
    Helped
    3764 / 3764
    Points
    81,905
    Level
    69

    Re: how to boost microvolts to higher voltages?

    Hi,

    these are the values i got. is this noninverting amplifier working?
    But the Opamp in most of your cases is overdriven.

    There are many Opamp circuit tutorials, even videos in the internet.
    Use them, they are for free. You urgently need to learn basics on your own. A forum can't replace school.

    Also there are free simulator tools.
    Then you can play around, measure every voltage and current without time consuming soldering.
    *****

    Let's just calculate through one example. Let's take the 1000 ohms, 1000 ohms resistors.
    * supply voltage is 7.79V (this violates your Opamp's specifications, because it should be at least 8V. --> see "Operating Voltage" )
    * voltage at +IN node is 0V (this means that this input is connected to a supply rail. This violates your Opamp's specification, because your's is no Rail-to-rail input type.--> see "Input Common Mode Voltage Range")
    But let's assume from here on you use a suitable Opamp:
    * Rf = 1000 Ohms
    * Rin = 1000 Ohms
    * V_inp = input voltage is = (V_ Rin - V_+In) = 1.45V - 0V = 1.45V

    --> A = gain = - Rf / Rin = - 1000 Ohms / 1000 Ohms = -1

    The expectable V_out = V_+In + gain × V_inp = 0V + (-1) × 1.45V = -1.45V.
    ( This violates your Opamp's specification. --> see "Maximum Output Voltage Swing")
    -1.45V is beyound your supply rails. No opamp can output voltage beyond it's supply rails.
    --> thus it is expected to saturate close to negative rail.

    You may simplify your life with using eXcel for such calculations.

    Klaus
    Please don´t contact me via PM, because there is no time to respond to them. No friend requests. Thank you.


    1 members found this post helpful.

--[[ ]]--