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Operational amplifiers

Discussion in 'Electronics Homework Help' started by Mbetts, Feb 22, 2013.

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  1. Mbetts


    Feb 22, 2013
    Hi guys I recently started a degree in electronic and electrical engineering I come from an advanced apprenticeship background and I'm not the best mathes student.

    My lecturer gave me the worksheet pictured.

    I used the formula as follows for calculating inverted and non inverted amplifiers.

    Inv: Vo R2
    --- = - ---
    Vi R1

    Non-inv: Vo R2
    --- = 1 + ---
    Vi R1

    I transposed the inverted op amp formula and got all the answers right. Got onto the non-inverting op amp and got most of the answers right except the R2 ohmage. Do you think this is his typo or am I wrong (I'll put my thought process down.)

    (Vo )
    (--- - 1) X R1 = R2
    (Vi )

    With this in mind.

    (11.75 )
    (------- -1) x 1000 = 46k
    (0.250 )

    Any help or guidance is greatly appreciated also any sites and books I could read?


    Attached Files:

  2. Laplace


    Apr 4, 2010
    R2=46K is the correct answer. But how can you be sure?

    Look at the schematic for the non-inverting amplifier. Realize that whenever an (ideal) op amp is in its linear operating range the voltage at the '+' and '-' inputs has exactly the same value. Here the voltage at the '-' input is the result of a voltage divider from Vo so the equation V'+'=V'-' gives 0.25=11.75(1/(1+46)). You know your answer is correct if 11.75/47=0.25
  3. Mbetts


    Feb 22, 2013
    Thanks for the reply.

    You are the second person to have confirmed this for me I used stand the op amps input works with the output the create a ratio that gives the output when working Vo anyways I understand a bit better now,
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