1. Op-Amp Explorations Mike Farrell 3/30/2011

2. Outline Goals and Setup Op-Amp Input current Simple Inverting Amp Simple Non-Inverting Amp Combine the two Non-Ideal Analysis

3. Goals Prove that the ideal Op-Amp model is valid Prove that the non-ideal model is more accurate but not necessary. Demonstrate how to hook up Op-Amp circuits

4. Setup All Circuits use a LM741C opamp Power Supply is +- 15V Ideal Constraints –In=Ip=0 –Vn=Vp –Av=Inf –Rin=Inf –Ro = 0

5. Op-Amp Input Current Circuit

6. Input Current Results Measured Vp and Vn. I=(0-Vx)/100K (Passive Sign Convention) All measurements are within spec for data sheet and very close to ideal. Ideal741 Data Sheet Measured Vp (mV)0-4.34 Vn (mV)0-4.56 Ip (nA)080nA typ 500nA max 43.4 In (nA)045.6

7. Inverting Op-Amp Circuit

8. Non-Inverting Op-Amp Circuit

9. Non-Inverting/Inverting Results InvertingNon-Inverting Ideal (V) Measured (V) % ErrorIdeal (V) Measured (V) % Error Vp3.00 2.99.333 3.002.971.00 Vn3.002.98.6673.002.99.333 Vout-7.50-7.54.5337.507.48.667

10. Combo Op-Amp Circuit Combination of Inverting and Non-Inverting Amplifiers

11. Combo Op-Amp Results with Non- Ideal Calculations IdealMeasuredNon-Ideal Model -- Calculated (V) % Error (V)% Error Vp3.00 2.99.333 3.000 Vn3.002.98.6673.000 Vout023.2m--.397u--

12. Non-Ideal Circuit used for Calculations

13. Conclusions In and Ip <50nA (~0A) Vn = Vp Using realistic Av, Rin, and Ro does not have a significant effect on voltage error. Vout errors all less than 1% from ideal

14. Slide 14 Questions?