PSpice model of a compensated op amp

EE446 Report

To: P.J. Galvin, R.J Shoop and M.E. Turk

From: (1, 2 or 3 person teams)

Date: 2/25/08

Subject: PSpice model of the TL054 op amp

Introduction: The circuit shown in Figure 1 is proposed as a model of a compensated op amp. This model incorporates the input and output impedances of the op amp and the open loop gain of a compensated op amp:

where a_o is the dc gain, f_t is the unity-gain bandwidth and v_o is the node voltage at the output node of the op amp.

Figure 1.Model of a Compensated Op Amp

The parameters of the model are related to the parameters of a compensated op amp by the equations

R_i =… , A = … , R = … , C = … and R_o = …

Conclusion: …

Results:

R1: The parameters of the TL054 op amp are …. Using the equations given in the introduction, the parameters of the model of the TL054 op amp are ….

R2: The plot of v_o as a function of v_D shown in Figure 2 was obtained using the PSpice simulation shown in Figure 3…

R3: The simulation indicate that …

Using Superposition the Partition the Task

Janet Howells, Michael Kubeja, Russell Shoop, John Stevens and Michelle Turk:

EE446 Report

To:

From:

Date:

Subject: Response to bias current Ib1 in the Instrumentation Circuit

Introduction: Consider the circuit shown in Figure 1

Figure 1.

Conclusion: The output voltage, v_o, of the circuit shown in Figure 1 input current I_B1 by the equation …

v_o = …

Results:

R1: The equation relating v_o and I_B1 is derived as follows: …

Finally

v_o = …

R2: The plot of v_o as a function of I_B1 show in Figure 2 was obtained using the PSpice simulation shown in Figure 3…

R3: The simulation agrees with the equation because …

Patrick Galvin, Dillon Hanley, Andrew Potocek, Joel Reeves and James Smith:

Michael Bonadonna, Thomas Herrington, Ryan Swanson, Adam Winterkorn and Gregory Zenger:

James DeMay, Andrew Foster, James Madison, Jonathan Marshall, Kurtis Rooks and Kurt Roskopf:

Op Amp Offset Voltage and Current

EE446 Report

To: J.A. Svoboda

From:

Date:

Subject: Effect of Op Amp Offset Voltage and Current on an Instrumentation Circuit

Introduction: The circuit shown in Figure 1 produces an output voltage, v_o, that represents the temperature T, in degree C, measured by the transducer. The nonideal op amp represents the LM 307 op amp manufactured by National Semiconductor Corporation (http://www.national.com/ds/LM/LM107.pdf#page=1&search=%22LM307%22).

Figure 1. A temperature transducer and amplifier.

Conclusion: After choosing R₃ = … to minimize the effects of the op amp offset, the maximum output offset voltage is e_os = … which is equivalent to an input temperature of T = …

Results:

R1: Accounting for the offsets introduced by the op amp, the output voltage is given by

v_o = …

R2: After choosing R₃ = … to minimize the effects of the op amp offset, the maximum output offset voltage is

e_os = …

R3: The maximum output offset voltage is equivalent to an input temperature of T = …

Findings:

F1.1 The nonideal op amp is modeled as shown in Figure 2.

Figure 2. Op Amp Model

F1.2 The specifications for a LM307 op amp at room temperature indicate that | v_os | < …, | i_B | <…, and | i_os | < ….

F1.3 Replacing the nonideal op amp by its model gives the circuit shown in Figure 3.

Figure 3.

F1.4 Using superposition (provide derivation), the output voltage of the circuit shown in Figure 3 is found to be

v_o = …

F2.1 To minimize the effects of the offsets, choose R₃ …. (Provide derivation showing how to choose resistance R₃.) Then, choose R₃.

F2.2 After choosing R₃ = … to minimize the effects of the op amp offset, the maximum output offset voltage is

e_os = …

F2.3 The PSpice simulation shown in Figure 4 confirms this value of output offset voltage.

Figure 4. Replace this Figure with your simulation.

F3.1 The maximum output offset voltage is equivalent to an input temperature of T = …