Op-Amps II

Op Amps II

Purpose: To observe the effects varying the feedback and input resistances in an op amp circuit.

In order to determine what resistors to use calculations were performed to obtain a gain of 10 and 0.1mA current.

 The circuit was then built and Vs was adjusted to 0.25 V using a voltage divider as shown.

A 1kΩ resistor was then  placed as the load.

Voltages were then recorded across all resistors using this set-up.

The following data was obtained

For V_IN = 1V 

       Measured I_cc = 0.867 mA 

                Calculated P_cc = 12*0.867 mP = 10.404 mP

       Measured I_ee = -0.979 mA 

                 Calculated P_ee = 12*0.979 mP = 11.748 mP

       I_cc + I_ee = 0.112 mA

       The percent error is 12% therefore, it is consistent with KCL.

  For V_IN = 1V 

    Measured I_cc = 0.877 mA 

            Calculated P_cc = 12*0.877 mP = 10.524 mP

    Measured I_ee = -0.984 mA 

             Calculated P_ee = 12*0.984 mP = 11.808 mP

     I_cc + I_ee = 0.107 mA

     The percent error is 07% therefore, it is consistent with KCL

Finally,  With percent errors of 12% and 7% this experiment is considered a success and obeys Kirchhoff's Current Law. We saw that the gain depends directly on Rf/Ri.