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Gain Bandwidth Product

Gain Bandwidth Product. Op-Amp. P in. P out. P DC. Gain Bandwidth Product. Think in terms of Energy Conservation. P out – P in ≤ P DC. Gain Bandwidth Product. P out – P in ≤ P DC.

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Gain Bandwidth Product

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  1. Gain Bandwidth Product

  2. Op-Amp Pin Pout PDC Gain Bandwidth Product Think in terms of Energy Conservation Pout – Pin≤ PDC

  3. Gain Bandwidth Product Pout – Pin≤ PDC Now consider Power expressed in the Frequency Domain as the Power Spectral Density Function, S(ω), and the Gain of the Op-Amp expressed as a function of Frequency, G(ω). ∫ G(ω) S(ω) dω - ∫ S(ω) dω≤ PDC Pout – Pin≤ PDC

  4. Gain Bandwidth Product Next, the expression ∫ G(ω) S(ω) dω - ∫ S(ω) dω≤ PDC simplifies to ∫ [G(ω) – 1] S(ω) dω≤ PDC and for large G(ω) ∫ G(ω) S(ω) dω≤ PDC

  5. Gain Bandwidth Product ∫ G(ω) S(ω) dω≤ PDC • Next assume: • amplifier bandwidth is BW • amplifier Gain (G) is constant over BW • signal spectra (S) is constant over BW G(ω) S(ω) = G x S x BW G x BW ≤ PDC / S

  6. Gain Bandwidth Product G x BW ≤ PDC / S constant term  Gain Bandwidth Product • Therefore if • G increases, BW must decrease, or • BW increases, G must decrease.

  7. Gain Bandwidth Product G x BW ≤ PDC / S constant term  Gain Bandwidth Product If G = 1, then BW = “Unity-gain Bandwidth”

  8. If G = 1, then BW = “Unity-gain Bandwidth”

  9. TL084 Unity-gain Unity-gain Bandwidth

  10. TL084 Open loop gain Unity gain Unity-gain Bandwidth

  11. VE = VIN+ - VIN- VOUT = a * VE VIN- VIN+

  12. The available DC power to the amplifier can either be put to use as high signal gain over a limited bandwidth or limited gain over a wide bandwidth.

  13. For fixed DC input power, the greatest signal gains are achieved with weak input signals. To get high gains in already amplified signals (as in output stages), increased amounts of DC power must be used.

  14. a (V+ - V-) Differential Amplifier Circuit Analysis

  15. a (V+ - V-) Differential Amplifier Circuit Analysis

  16. a (V+ - V-) Differential Amplifier Circuit Analysis

  17. a (V+ - V-) Differential Amplifier Circuit Analysis

  18. a (V+ - V-) Differential Amplifier Circuit Analysis  ZF/ ZG

  19. v1 v1 vid / 2 v2  vid / 2 vicm v2 Model of inputs with common-mode and differential-mode components Original Inputs vi1 vi2 Common Mode Rejection Ratio

  20. Common Mode Rejection RatioCMRR whereAis the differential mode gain andAcmis the common mode gain Ideally:CMRR Typically: 60 dB  CMRR  120 dB

  21. Assumes R2 = R4 and R1 = R3

  22. Differential Amplifier Circuit Analysis with Component Imbalance

  23. Differential Amplifier Circuit Analysis with Component Imbalance

  24. - Ro vo Rd vd ii + io Avd - vi RL + CL Input and Output Impedances of Noninverting Op-amp Configuration The unity gain buffer input impedance is much higher than the op-amp input impedance Rd. The amplifier output impedance is much smaller than the op-amp output impedance Ro.

  25. The available DC power to the amplifier can either be put to use as high signal gain over a limited bandwidth or limited gain over a wide bandwidth.

  26. high signal gain over a limited bandwidth or limited gain over a wide bandwidth. G=10,000 G=10 G=10 G=10 G=10

  27. R2 R2 vref R3 R3 R4 R4 v1 v2 vout R1 Instrumentation Amplifier

  28. R2 R2 vref R3 R3 R4 R4 v1 v2 vout R1 Instrumentation Amplifier Example Burr-Brown INA118 Parameters: Gain:

  29. ECG Amplifier System

  30. ECG Amplifier System Multiple Subsystems

  31. ECG Amplifier System Input Instrumentation Amplifier

  32. R2 R2 vref R3 R3 R4 R4 v1 v2 vout R1 Instrumentation Amplifier

  33. ECG Amplifier System Intermediate Filter and Amplifier

  34. Low-Pass with G=200 High-Pass ECG Amplifier System Intermediate Filter and Amplifier

  35. ECG Amplifier System Analog-to-Digital Converter

  36. ECG Amplifier System Zero Reference Bias Circuit

  37. ECG Amplifier System High-pass Filter for Autozeroing of DC Offset

  38. ECG Amplifier System CMRR Boost Circuit (Negative Common Mode Signal Injection on Subject’s Right Leg)

  39. ECG Amplifier System CMRR Boost Circuit (Negative Common Mode Signal Injection on Subject’s Right Leg)

  40. Common Mode Rejection RatioCMRR whereAis the differential mode gain andAcmis the common mode gain Ideally:CMRR Typically: 60 dB  CMRR  120 dB

  41. ECG Amplifier System

  42. R2 R2 C R3 R3 R4 R4 R v1 v2 vout 2R1 Instrumentation Amp A feedback network may also be included with the instrumentation amplifier. vdiff = v2 - v1

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