explaining circuit

Discussion in 'General Electronics Chat' started by Bill David, Oct 23, 2012.

  1. Bill David

    Thread Starter New Member

    Oct 23, 2012
    5
    0
    Hi all

    the attached picture shows the internal circuit of an operational amplifier LM324.

    it actually measures the difference of voltage between 2 inputs.

    can anyone of you help me with explaining how does the process of measuring this difference take place ?

    Thank you
     
  2. kubeek

    AAC Fanatic!

    Sep 20, 2005
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  3. electron_prince

    Member

    Sep 19, 2012
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    start with differential amplifier.
     
  4. ScottWang

    Moderator

    Aug 23, 2012
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    The theory similar like Seesaw.

    You can measure the V,I of the circuit.

    Rc1,Rc2 use 10K. (Rc1-Q1,Rc2-Q2)
    Re1,Re2 use 100Ω. (Re1-Q1,Re2-Q2)
    R1=1K
    Input1 → 22K → VR1M1 → +Vcc
    Input2 → 22K → VR1M2 → +Vcc
    +Vcc → +5V
    -Vee → GND
    VR1M1,VR1M2 - Variable resistor.

    You could adjust the VR1M1, not adjust VR1M2, and measure the following Voltage, and calculating the current.
    Adjust VR1M2, not Adjust VRM1, and measure the following Voltage, and calculating the current.

    Vc2_Q2=
    V_Rc1=
    V_Rc2=
    V_Re1=
    V_Re2=
    V_R1=

    I_Rc1=V_Rc1/10K=
    I_Rc2=V_Rc2/10K=
    I_Re1=V_Re1/100Ω=
    I_Re2=V_Re2/100Ω=
    I_R1=V_R1/1K=

    You can also change the resistors to the other values, and then adjust VR1M1,VR1M2, and do the measuring as above.

    If you want to measure more value, then you can change +Vcc to 9V,12V,15V...30V
     
    Last edited: Oct 24, 2012
  5. ramancini8

    Member

    Jul 18, 2012
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    The schematic is not for a lm324 because the transistors are NPN.
     
  6. kubeek

    AAC Fanatic!

    Sep 20, 2005
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    The original schematic is not for anyhting because no opamp is that simple.
     
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