Inverting Voltage Amplifier

Inverting Voltage Amplifier

In this lab, we wire the circuit above using an inverting voltage amplifier, OP27. We design the circuit in a way that the output is fed back in to the -in through a resistor double that of the -in resistor. We used 3.6 kΩ and 1.8 kΩ resistors which were measured at 3.51 kΩ and 1.76 kΩ, respectively.

The inverting voltage amplifier works according to the equation V_out = - (R2/R1)*V_in. Since R2 is double that of R1, this equation reduces to V_out = -2*V_in.

We use the data sheet from Analog Devices manufacturer to find the pin configuration diagram and wire the circuit accordingly. We use Analog Discovery to provide the 5+, 5-, and V_in supplies. Using a multimeter, we measure the output voltage, V_out and record the values. The input voltage is varied from -3.0 V to 4.0 V in 0.5 V increments. The data is shown below.

 Plotting output voltage vs input voltage we obtain the graph above. We see that there are saturation regions at -2.5 V and +2.5 V. In the center there is a linear region whose slope -1.97. If we rearrange the equation mentioned earlier, V_out = -2*V_in becomes V_out/V_in = -2 which is basically what the linear region in this graph represents (this is the gain). We obtained -1.97 instead of 2, which gives us a % error of  1.5%. The saturation regions are also of interest. We see that saturation occurs at +/- 2.5 V. When these voltages are doubles, we get +/- 5V which correspond to the +V and -V applied (+/- 5 V).