際際滷

際際滷Share a Scribd company logo

noise experiment

R
Ray Wang

1. The document describes experiments measuring noise in a preamplifier and transistor in the frequency domain as the cutoff frequency and temperature are varied. 2. Observations show that the thermal noise from the preamplifier is constant but thermal noise from the input varies with cutoff frequency. The plateaus need adjustment to analyze noise sources. 3. Measurements at different temperatures from 73F to 93F show that noise depends strongly on temperature at low frequencies and is independent at high frequencies, suggesting the noise comes from the channel at low frequencies and the resistor at high frequencies.

1 of 19
Download to read offline
Noise Experiments Ray Oct 13th, 2015
Preamp Analysis frequency domain Procedure: 1. Set its gain to 500V/V, input to gnd 2. Change the cutoff frequency of low-pass 鍖lter in preamp to see its output spectrum Observations: 1. Independent of the cutoff frequency, the high frequency thermal noise is always around -81dBVrms 2. When the cutoff frequency is between 1KHz to 10KHz, there are two plateaus with the second one as -81dBVrms
Preamp Analysis frequency domain cont. Conclusions: 1. Since the thermal noise in the 鍖rst plateau is from the preamp input while the second is from preamp itself, we need to adjust the cutoff frequency to make the 鍖rst plateau appear. 2. Also, we need the 鍖rst plateau to be as long as possible to get rid of the roll-off effect from either 鍖icker noise and preamp cutoff frequency. 1/f noise thermal noise due to preamp input thermal noise due to preamp fL
Noise Analysis frequency domain Measurement Setup: A To Spectrum Analyzer Preamp 1Mohm VGS
Noise Analysis frequency domain RD VGS Weak Inversion Condition
Noise Analysis frequency domain Setup detail: 1. No pole introduced in preamp 2. Device works in room temperature 73F 3. VGS=0.4V Pole (detector induced*)
Noise Analysis Integration Method Pole in preamp: 10Hz 1/f noise dominant
Noise Analysis Integration Method
Noise Analysis Integration Method
Noise Analysis Integration Method Pole in preamp: 10KHz thermal noise dominant Rload=1Kohm
Noise Analysis Integration Method
Noise Analysis Integration Method
Noise Analysis Integration Method Region 1 Region 2
Noise Analysis Integration Method Region 1: 1. noise highly depends on the temperature 2. This temperature dependence is from the channel noise Region 2: noise is almost independent of the temperature This happens because RD sits outside oven. No matter what is the reason, measuring temperature from 73F to 83F can tell us the channel noise dependence on the temperature
Noise Analysis vs Temperature frequency domain T=73F(296K) After averaging using two frequencies and 鍖ve resetting, -55.023 dBVrms noise power spectrum density is derived and it equals to 3.146uV/sqrt(Hz). Since preamp gain is 500V/V, the equivalent noise spectrum density from the detector is 3.146u/sqrt(500), which is 0.1407uV/sqrt(Hz) fL = 56.5KHz
Noise Analysis vs Temperature frequency domain T=83F(301.5K) After averaging using two frequencies and 鍖ve resetting, -53.872 dBVrms noise power spectrum density is derived and it equals to 4.1uV/sqrt(Hz). Since preamp gain is 500V/V, the equivalent noise spectrum density from the detector is 4.1u/sqrt(500), which is 0.18336uV/sqrt(Hz) fL = 47.616KHz
Noise Analysis vs Temperature frequency domain T=93F(307K) After averaging using two frequencies and 鍖ve resetting, -53.792 dBVrms noise power spectrum density is derived and it equals to 4.1764uV/sqrt(Hz). Since preamp gain is 500V/V, the equivalent noise spectrum density from the detector is 4.1u/sqrt(500), which is 0.18677uV/sqrt(Hz) fL = 45.4KHz Noise actually drops in this temperature
Noise Analysis vs Temperature frequency domain theoretic result Channel Noise Loading resistance noise Frequency domain experiment result:
Noise Analysis vs Temperature frequency domain theoretic result Channel Noise Weak inversion approximation Loading resistance noise Flicker Noise Channel Noise strong inversion approximation Frequency domain experiment result:

More Related Content

noise experiment

  • 2. Preamp Analysis frequency domain Procedure: 1. Set its gain to 500V/V, input to gnd 2. Change the cutoff frequency of low-pass 鍖lter in preamp to see its output spectrum Observations: 1. Independent of the cutoff frequency, the high frequency thermal noise is always around -81dBVrms 2. When the cutoff frequency is between 1KHz to 10KHz, there are two plateaus with the second one as -81dBVrms
  • 3. Preamp Analysis frequency domain cont. Conclusions: 1. Since the thermal noise in the 鍖rst plateau is from the preamp input while the second is from preamp itself, we need to adjust the cutoff frequency to make the 鍖rst plateau appear. 2. Also, we need the 鍖rst plateau to be as long as possible to get rid of the roll-off effect from either 鍖icker noise and preamp cutoff frequency. 1/f noise thermal noise due to preamp input thermal noise due to preamp fL
  • 4. Noise Analysis frequency domain Measurement Setup: A To Spectrum Analyzer Preamp 1Mohm VGS
  • 6. Noise Analysis frequency domain Setup detail: 1. No pole introduced in preamp 2. Device works in room temperature 73F 3. VGS=0.4V Pole (detector induced*)
  • 7. Noise Analysis Integration Method Pole in preamp: 10Hz 1/f noise dominant
  • 10. Noise Analysis Integration Method Pole in preamp: 10KHz thermal noise dominant Rload=1Kohm
  • 14. Noise Analysis Integration Method Region 1: 1. noise highly depends on the temperature 2. This temperature dependence is from the channel noise Region 2: noise is almost independent of the temperature This happens because RD sits outside oven. No matter what is the reason, measuring temperature from 73F to 83F can tell us the channel noise dependence on the temperature
  • 15. Noise Analysis vs Temperature frequency domain T=73F(296K) After averaging using two frequencies and 鍖ve resetting, -55.023 dBVrms noise power spectrum density is derived and it equals to 3.146uV/sqrt(Hz). Since preamp gain is 500V/V, the equivalent noise spectrum density from the detector is 3.146u/sqrt(500), which is 0.1407uV/sqrt(Hz) fL = 56.5KHz
  • 16. Noise Analysis vs Temperature frequency domain T=83F(301.5K) After averaging using two frequencies and 鍖ve resetting, -53.872 dBVrms noise power spectrum density is derived and it equals to 4.1uV/sqrt(Hz). Since preamp gain is 500V/V, the equivalent noise spectrum density from the detector is 4.1u/sqrt(500), which is 0.18336uV/sqrt(Hz) fL = 47.616KHz
  • 17. Noise Analysis vs Temperature frequency domain T=93F(307K) After averaging using two frequencies and 鍖ve resetting, -53.792 dBVrms noise power spectrum density is derived and it equals to 4.1764uV/sqrt(Hz). Since preamp gain is 500V/V, the equivalent noise spectrum density from the detector is 4.1u/sqrt(500), which is 0.18677uV/sqrt(Hz) fL = 45.4KHz Noise actually drops in this temperature
  • 18. Noise Analysis vs Temperature frequency domain theoretic result Channel Noise Loading resistance noise Frequency domain experiment result:
  • 19. Noise Analysis vs Temperature frequency domain theoretic result Channel Noise Weak inversion approximation Loading resistance noise Flicker Noise Channel Noise strong inversion approximation Frequency domain experiment result: