1 / 22

Oklahoma State University

Oklahoma State University. Amplifier Noise Seminar 2:30 Friday Sept 10 Presented by : Dr. Chris Hutchens. Oklahoma State University. Amplifier Noise Seminar 2:30 Friday Sept 10 Presented by : Dr. Chris Hutchens. MOS Noise Sources. Noise Spectrical Density. Noise Spectrical Density.

thuong
Télécharger la présentation

Oklahoma State University

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. Oklahoma State University Amplifier Noise Seminar 2:30 Friday Sept 10 Presented by: Dr. Chris Hutchens

  2. Oklahoma State University Amplifier Noise Seminar 2:30 Friday Sept 10 Presented by: Dr. Chris Hutchens

  3. MOS Noise Sources

  4. Noise Spectrical Density

  5. Noise Spectrical Density

  6. Noise Spectrical Density - design

  7. Noise - Shot “Thermal” in Resistors Resistors - A2/Hz   Multiple x R2 V2/Hz 1K 4.0 nV/Hz To find total equivalent noise

  8. Noise - Shot “Thermal” BW To find total equivalent noise For a single pole system if f1 << f2 then

  9. Noise - Shot “Thermal” BW – kT/C For a single pole system if f1 << f2 the equivalent effective equals f3dB /2 kT/C applies to all 1st Order systems!!!

  10. MOS Noise Filtered

  11. MOS Noise Filtered – 1/f

  12. MOS Noise Filtered – 1/f

  13. Noise in Amplifiers Noise - Shot “Thermal”and 1/f MOS - “1/f” Diodes I2d(f) = 2q ID “Shot” rd = Vt/ nID “ No noise” Where  represents an equivalent number of transistor or the composite number for the amplifier. Ideal Amp with noise sources added Resistors -   1K 4.0 nV/Hz

  14. MOS Summary • Active MOS device currents can be converted to a equivalent input voltage by dividing by gm2. k = Boltzmans Constant • V2iT(f) = K/ {WLCoxf} + {4kT (2/3)} /gm • The composite noise of all MOS devices is represented by  V2iT(f) = f K/ {WLCoxf} + {4kT t (2/3)} /gm

  15. Resistive source impedance vineqequivalent noise voltage (in V/Hz) vnamp input noise voltage (in V/  Hz) inamp input noise current (in A/  Hz) RSsignal source impedance. k constant of Boltzmann, 1.38 × 10-23 J/K T absolute temperature K.

  16. A practical schematic of an inverting opamp circuit Observed dependency on RS, results in the non-inverting configuration being preferred. For FET amp

  17. Resistive and capacitive source impedance (more practical.) where RF and RI have been selected sufficiently such that their noise contributions maybe neglected. Where K = RF/RI + 1 and Cin includes all the parasitic capacitance at the noninverting node. For FET amp

  18. Intermediate Summary Comparing (1) and (5) one observe that the equivalent input noise is frequency depended. The higher the frequency the greater the contribution of vngets. This requires that filtering be done at the output of the first gain stage to avoid the noise peaking. Further from (4) it can be observed that the signal bandwidth may be limited by Cin.

  19. Charge measurement with a voltage amplifier Where K = RF/RI + 1 and Cp is all additional parasitic capacitance at the noninverting node. Note Q(s) equals is the derivative of the current or; Q(s) = I(s)/s. (7)

  20. Charge measurement with a voltage amplifier The input equivalent noise current is found as follows:   (8) Appling s Q(s) = I(s).   (9a) For FET amps   (9b) where RF and RI have been selected such that their noise contributions maybe neglected and Cin equal CSensor plus Cp.

  21. Current measurement with a current amplifier Adding Feedback time constant RF CF results in band limits both signal and noise. (10) (11a) For FET amps (11b)

  22. Current measurement with a current amplifier Applying (7) to (11) (10b) (12a) For FET amps (12b) Adding Feedback time constant RF CF results in band limits of both signal and noise.

More Related