Noninverting Amplifier


The circuit shown below is called an noninverting amplifier. The op amp in this circuit must be biased using DC voltage sources. (As is conventional, these DC sources are not shown in the drawing of the inverting amplifier. None-the-less, the sizes of these dc sources determine the voltage at which the op amp saturates.) In this example, volt sources were used. As a consequence, the op amp saturates at volts.

When the op amp is not saturated, the inverting amplifier produces an output voltage, Vo, that is proportional to the input voltage, Vs. The output voltage is measured using a voltmeter. The input voltage is the voltage of the voltage source. The constant of proportionality is called the gain of the inverting amplifier. The value of the gain of the inverting amplifier is determined by the resistances, Ri and Rf, of the two resistors in the noninverting amplifier.


The values of the input, Vs, and of the resistances, Ri and Rf, can be adjusted using the scroll bars.



Challenges:

  1. Set Ri = 20000 and Rf = 40000. Adjust Vs so that Vo = 12.0.

  2. Set Ri = 20000 and Rf = 40000. Adjust Vs so that Vo = -12.0.

  3. Set Ri = 15000 and Rf = 45000. Determine the range of output voltage that can be obtained by adjusting the input voltage.

  4. Set Ri = 15000 and Rf = 45000. Determine the range of input voltages that do not cause the op amp to saturate.

  5. Set Ri = 20000 and Vs = 5. Predict the value of Rf required to cause Vo = 7.5. Use the scrollbars to check your prediction.

  6. Set Ri = 20000 and Vs = 5. Determine the range of output voltage that can be obtained by adjusting the resistance Rf.

  7. Set Rf = 25000 and Vs = 5. Predict the value of Ri required to cause Vo = 7.5. Use the scrollbars to check your prediction.

  8. Set Rf = 25000 and Vs = 5. Determine the range of output voltage that can be obtained by adjusting the resistance Ri.

  9. Set Vs = 4. Adjust Ri and Rf so that Vo = -6.

  10. Adjust Ri and Rf so that Rf = 2*Ri. Measure the value of the gain of the inverting amplifier.

  11. Adjust Ri and Rf so that Ri = 2*Rf. Measure the value of the gain of the inverting amplifier.

  12. Adjust Ri and Rf so that Rf = Ri. Measure the value of the gain of the inverting amplifier.

  13. Adjust Ri and Rf so that the value of the gain of the inverting amplifier is 2.8.

  14. Determine the largest value of gain that can be obtained when Rf < Ri.