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1/f measurement of uA741 opamp

Yuvraj Pundkar
Prodigy 85 points

To 

Art Kay

Respected Sir

              I am a MTech student. I read your presentation on noise measurement. I am doing similar kind of noise measurement. My task is to measure 1/f noise of various opamps. So I started with uA741 opamp. I followed your steps as described in presentation. I am using LabView 11 for automation and Agilent's Dynamic Signal Analyzer 35670A for measurement. Data sheet value of 741 opamp noise is 32 nV/rtHz at 100Hz and values which I obtained(in one set of readings) is 98nV/rtHz at 100Hz.  
              Regarding this experiment I have some questions...
1. Right now I am doing all my calculations on circuit assembled on breadboard. I am using battery as a power supply. Main problem I am facing is 50 Hz noise. I am getting similar peaks even at 100 Hz, 150Hz, 200 Hz (multiples of 50Hz). I think these are coming through Agilent's 35670A. How to get rid of these? I did measurement by ignoring these peaks. But sometimes it affects the adjacent frequencies (sometimes from 35 to 55 Hz). So I have to ignore complete span of frequencies. 
2. Data sheet graph of 741 shows calculation from 100 Hz frequency where as 1/f noise is dominant at lower frequencies. I did the measurement starting from 100 Hz so that I can verify the values. How can I get more accurate values of 1 by f noise?
3. I am planning to do the measurement on the circuit assembled on PCB with BNC cables. Also will the 0.1 Hz to 10 Hz filter you specified in presentation help in getting accurate values? Are such filters commercially available??? or do i will have to assemble it on PCB??
4. Sometimes the noise level shoots up to few micro volts at low frequencies. I searched the local market for 20 uF ceramic capacitor(required at the input onf analyzer)  but couldn't find one. So i bought the electrolytic one.  Then i replaced the same with 47nF ceramic capacitor. Then again repeated the measurement by replacing the capacitor with LPF (single RC with R = 1M ohm, and C= 47 nF) then with HPF with same RC. So can you advise me which way is correct?? 
Do advise whatever steps I followed are correct or not and what more can be done in this case. 
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Regards,
Yuvraj Pundkar
Mtech Student at Viswesvarya National Institute of Technology,
Nagpur, Maharashtra, India.