1 / 52

Frequency Response of Amplifier

Frequency Response of Amplifier. Jack Ou Sonoma State University. RC Low Pass (Review). A pole: a root of the denomintor 1+sRC=0→S=-RC. Laplace Transform/Fourier Transform. (Laplace Transform). Complex s plane. | +p|. (Fourier Transform). -p. p=1/(RC).

tracey
Download Presentation

Frequency Response of Amplifier

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Frequency Response of Amplifier Jack Ou Sonoma State University

  2. RC Low Pass (Review) A pole: a root of the denomintor 1+sRC=0→S=-RC

  3. Laplace Transform/Fourier Transform (Laplace Transform) Complex s plane |+p| (Fourier Transform) -p p=1/(RC) Location of the zero in the left complex plane )|=1/|+p| Phase=-tan-1(/p)

  4. Rules of thumb: (applicable to a pole) Magnitude: 20 dB drop after the cut-off frequency 3dB drop at the cut-off frequency Phase: -45 deg at the cut-off frequency 0 degree at one decade prior to the cut-frequency 90 degrees one decade after the cut-off frequency

  5. RC High Pass Filter (Review) A zero at DC. A pole from the denominator. 1+sRC=0→S=-RC

  6. Laplace Transform/Fourier Transform (Laplace Transform) Complex s plane |+p| (Fourier Transform) -p p=1/(RC) Zero at DC. Location of the zero in the left complex plane )|=||/|+p| Phase=90-tan-1(/p)

  7. Zero at the origin. Thus phase(f=0)=90 degrees. The high pass filter has a cut-off frequency of 100.

  8. RC High Pass Filter (Review) R12=(R1R2)/(R1+R2) A pole and a zero in the left complex plane.

  9. Laplace Transform/Fourier Transform (Low Frequency) (Laplace Transform) Complex s plane |+p| |+z| (Fourier Transform) -p z=1/(RC) p=1/(R12C) -z Location of the zero in the left complex plane At low frequencies, |+p|>|+p|.

  10. Laplace Transform/Fourier Transform (High Frequency) (Laplace Transform) Complex s plane |+z| |+p| (Fourier Transform) -p z=1/(RC) p=1/(R12C) -z Location of the zero in the left complex plane At high frequency, |+p|is almost equal to |+p|.

  11. Design • ωz=1/R1C • ωp=1/(R12)C • Note that R12<R1 • If R2<<R1, ωp/ ωp=R1/R2 • Design for ωp/ ωp=1000

  12. High Frequency

  13. Examples

  14. Source Follower

  15. Device Setup Gmoverid: Gm=17.24 mS RS=1000 Ohms GMBS=2.8 mS CGS=62.79 fF

  16. Small Signal Parameters Design Constraints: 1/(gm+gmbs)=50 Ohms Large R1 to minimize Q R2=58 Ohms R1=1102 Ohms L=4.013 nH

  17. Simulation Results

  18. Current Mirror Example

  19. Gm1=201.3uS GM3=201uS CGS3=CGS4=306.9fF GDS4=3.348uS GDS2=5.119uS Rload=118 Kohms Cload=1 pF Fp1=1.347 MHz Fp2=52.11 MHz Fz=104.2 MHz

  20. Magnitude AvDC,matlab=27.52 AvDC,sim=27.45 Fp1matlab=1.34MHz Fp1sim=1.23 MHz

  21. Phase

  22. Transit Frequency

  23. Transit Frequency Calculation

  24. Understanding Transit Frequency Since fT depends on VGS-VT, fTdepndes on gm/ID. fT depends on L.

  25. Overdrive Voltage as a function of gm/ID gm/ID=2/(VOV)

  26. Transit Frequency as function of gm/ID

  27. gm/gds as a function of gm/ID

  28. Trade-off of gm/gds and fT fT gm/gds gm/ID 15-20

  29. Numerical Example VDS=0.6 V

  30. Numerical Example VDS=0.6 V

  31. gm/ID Principle

  32. Use to gm/ID principle to find capacitance • gm/ID→(fT,I/W,gm/gds) • fT=gm/cgg, cgg=cgs+cgb+cgd • cgs/cgg is also gm/ID dependent.

  33. Example • Assume gm/ID=20, L=120 nm, VDS=0.6V, I=100uA. • fT=22.76 GHz • cgg=gm/fT=13.98 fF • cgd/cgg=0.29→cgd=4.1 fF • cgs/cgg=0.75 →Cgs=10.5 fF

  34. Noise

  35. Noise is not deterministic The value of noise cannot be predicted at any time even if the past values are known.

  36. Average Power of a Random Signal Periodic voltage to a load resistance. Observe the noise for a long time. It is customary to eliminate RL from PAV. Unit: V2 rather than W.

  37. Power Spectral Density Sx(f1) has unit of V2/Hz. PSD shows how much Power the signal carries at each frequency.

  38. PSD of the Output Noise

  39. PSD of the Output Noise

  40. Output Noise

  41. PSD of the Input Noise

  42. Input Noise

  43. Noise Shaping

  44. Correlated and Uncorrelated Sources Pav=Pav1+Pav2 Superposition holds for only for uncorrelated sources. (How similar two signals are.)

  45. Uncorrelated/Correlated Sources (Multiple conversations in progress) (clapping)

  46. Resistor Thermal Noise

  47. Example Vnr1sqr=2.3288 x 10-19 Vnr3sqr=7.7625 x 10-20 Vnoutsqr=3.1050 x10-19

  48. Analytical Versus Simulation

  49. as a function of length

  50. Corner Frequency (fco)

More Related