1. The electrocardiogram Op-amps, instrumentation amps, filters

2. This is your data V (arb) Time (sec)

3. EKG The EKG is a powerful diagnostic tool. Regularly used by cardiologists.

4. Disclaimers • We are not real doctors. Neither are you. Do not try to interpret your EKG.

5. Safety

6. Safety • We will review this in lab, but basically • 100 K resistors between you and breadboard. • Unplug your laptop while collecting data.

7. Privacy • Your EKG could be considered private medical information under Federal HIPAA laws. • If using this data makes you at all uncomfortable – then use one of the instructors as your subject.

8. The circuit AD623 – Instrumentation amplifier

9. The Op-Amp

10. Dynamic model of an op-amp

11. The op-amp follower

12. Dynamic model of the follower

13. Simplification for op-amp circuit analysis • If the op-amp is wired with negative feedback, and - • Changes are “slow” (less than ~100 kHz), then – • Assume no current flow through into the inputs. • The two input voltages are equal.

14. What does this circuit do?

15. What does this circuit do?

16. What does this circuit do?

17. The instrumentation amplifier Wikipedia

18. AD623 Data sheet

19. Let’s look at the filters now… Vout

20. Impedance (Z)General form of Ohm’s Law V = I Z Example: capacitor

21. RC circuit (via impedances) Voltage divider Vout

22. Do you remember how to plot Vout/Vin ? w = logspace(0,4,100); j = sqrt(-1); R = 10e3; C = 1e-6; Z1 = R; Z2 = 1./(j*w*C); loglog(w,abs(Z2./(Z1+Z2)));

23. Resistors in series and parallel Impedances in series: Impedances in parallel: Can you derive these relationships?

24. What about two filters in series? Vout Vin

25. The circuit