Keysight B2980A questions - Page 1
Forum section: electronics / testgear

author: vaualbus
author_rank: Frequent Contributor
timestamp: September 19, 2014, 12:13:50 am
content: Today I was searching around keysight eletronic's site (from me looks better that the agilent one) and come across this inbstrument:The agilent new B2980A femcto amper meter and ohm meter.It can measure up 0.01pA (0.01 * 10^-15 = 10aA) for current and up to 100Pohm (1 * 10^15) of resistence.Now my question is where you need to measeure this little current? And that high resistence?(I know that nowdays less use of current for circuit is great but op amp have leaks current of a uA not pA! and I don't think that a circuit can consume this extremly weak current either)The instrument is the new line of keysight instrument where they use a lcd and also produce graphs f the acquire values and other stuff.I wish to have some clarification and practical use of this instrument.

author: plesa
author_rank: Frequent Contributor
timestamp: September 19, 2014, 12:52:22 am
content: Quote from: vaualbus on September 19, 2014, 12:13:50 amThe instrument is not it is on a market for a while. The main competitor is Keithley 2600B SMU series.The main usage is for characterization of semiconductors.Main benefit is that these SMU are pretty versatile instrument ( low level measurement, power supply integrated, 4-quadrant operation, fast setting time, 6.5 meter), but quite expensive.If you need only low level measurement you can buy picoammeter (low input impedance) or electrometer ( high input impedance) cheaper.I'm using 2636B mainly for testing photo-diodes for photon detection.Instrument has embedded script interpreter which allows you to write your own scripts and run them.

author: Artraze
author_rank: Contributor
timestamp: September 19, 2014, 04:21:02 am
content: Just because I was curious, the 0.01fA (10^-17A) works out to be all of 62.5 electrons per second. That's pretty impressive. Puling up the spec, though, reveals an accuracy of only 0.5% + 3fA and requires 1.4s to settle. So much of that 0.01fA is derived from resolution and noise analysis / reduction.Anyways, op amps with < pA bias currents are not uncommon. For instance, consider the LMC6082, which is 10fA at room temperature, and about 2fA at 0C. Certainly you would want better than 1fA resolution to accurately characterize something <10fA.

author: plesa
author_rank: Frequent Contributor
timestamp: September 19, 2014, 06:56:00 am
content: I do not know what contains the 2636B input stage, the opamp which you mentioned is used on Keithley 6485/6487. I do not exactly remember but there is LMC6061 or LMC6081 and LMC 662 with 2fA input bias.

author: skrap
author_rank: Contributor
timestamp: September 19, 2014, 11:16:35 am
content: Quote from: vaualbus on September 19, 2014, 12:13:50 amThey are used extensively in semiconductor research laboratories. To name one application is for example when you want to characterize devices such as a MOS capacitor. You might for example want to see the leakage current through the gate stack and the dielectric where you have extremely high resistance and very low currents. Typically this process is automated so that a probe station goes through specifically designed test points all over the wafer to get a wafer-wide profile.Here is another thing of beauty:http://www.keithley.com/products/dcac/currentvoltage/4200scs/I really enjoy both the HP/Agilent and Keithley instruments, they are really awesome machines to have in the lab but I recon they are very niche products with very little use else where.

author: vaualbus
author_rank: Frequent Contributor
timestamp: September 19, 2014, 11:19:29 am
content: I really not this such of instrument but i was wonder about the uses. And also how they achivied such loe currents and high resistence.

author: skrap
author_rank: Contributor
timestamp: September 19, 2014, 11:43:15 am
content: Quote from: vaualbus on September 19, 2014, 11:19:29 amI'm sorry but I don't understand what you mean by this. I don't know what other parts of the industry would use it for, but the lab I frequently attend and many others I know of use them in nano technology related research extensively.If you want to know how it achieves this kind of performance there are plenty of handbooks which goes in to more details.Here is one:http://www.sel.eesc.usp.br/informatica/upload/jma/agilent/The%20Parametric%20Measurement%20Handbook%20-%20March%202012.pdfIf you want to look more into the exact kind of components in these kinds of instruments you have Daves teardown of the SMU and there are similar pictures available if you google a bit as well.