Where to Buy Low Inductance Resistor and Capacitor? - Page 1
Forum section: electronics / general

author: Mechatrommer
author_rank: Super Contributor
timestamp: April 12, 2012, 09:00:37 am
content: i cant see in digikey or ebay. can someone suggest good supplier for this low inductance passive component. main objective is for high frequency purpose. ayrton perry winding resistor? smd preferable, through hole is better than nothing. suggestion? thanks.

author: T4P
author_rank: Super Contributor
timestamp: April 12, 2012, 10:53:20 am
content: SMD Thin film resistors are low inductance .. no ?I think if you want high frequency caps , go for RF Caps .

author: Mechatrommer
author_rank: Super Contributor
timestamp: April 12, 2012, 11:29:38 am
content: Quote from: Dave.S on April 12, 2012, 10:53:20 amsmd or through hole in my stock are all "resonant filter", not low inductance low noise. can give me basic example of what an rf caps is? link?about the resistor, i read datasheet from site tti (vishay) and nicrom iirc just now, but it doesnt indicate what inductive value of them, they just say, low inductance, how low i've no idea.

author: free_electron
author_rank: Super Contributor
timestamp: April 12, 2012, 12:43:46 pm
content: Look at johanson dielectrics for good rf caps in smd.Low inductance resistors : susumu or epcos.They key is to go with thin film resistors.If , on digikeys site, you type 1M 0805 thin filmYou will already have narrowed it down.Difference between thin and thick film you ask ?Thick film is a carbon ink based process. Then they cut a meander to tune. Thin film is a metal vapor deposition . The tuning cut is different too.What frequencies are we talking and what resistance value ?

author: T4P
author_rank: Super Contributor
timestamp: April 12, 2012, 01:26:07 pm
content: http://my.element14.com/capacitors_rf

author: Mechatrommer
author_rank: Super Contributor
timestamp: April 13, 2012, 01:03:03 am
content: Quote from: free_electron on April 12, 2012, 12:43:46 pmnon inductive up to 50-100MHz. value typical 1K-10Mohm

author: ejeffrey
author_rank: Super Contributor
timestamp: April 13, 2012, 04:19:16 pm
content: I am pretty sure all surface mount resistors are non-inductive. Even if you wanted to it would be fairly difficult to cause substantial inductance. Same thing for SMD caps actually, although you want low loss dielectrics (i.e., C0G ceramics) to keep the impedance capacitive at high frequency.The inductance of these components comes primarily from the shape of the package itself, not anything to do with the resistor/capacitor, and from the PCB traces surrounding it, particularly vias. Smaller packages have less inductance. You can reduce inductance further by putting multiple elements in parallel, but you have to be careful to not add more inductance with traces and vias than you save.Quoteat 100 MHz, 1 nanohenry is 0.6 ohms. Typical parasitic inductances are measured in nanohenrys, and they will never be significant for a 1 kohm resistor. On the other hand, you will have to worry quite a bit about parasitic capacitance. SMD packages have typical parasitic capacitances of a few .1 pF. At 100 MHz, that is 16 kohm. So a 1 megaohm resistor will always be dominated by capacitance, and it is a non-negligible contribution even to a 1 kohm resistor.The easy way to remember this is that the typical characteristic impedance of a PCB trace is between 50 and 200 ohms. That is the impedance where the natural L and C characteristics balance out. At impedances above that you mostly worry about shunt capacitance. At lower impedances you care about series inductance.Edit: I should add that by "all surface mount" components I mean things like chip resistors and capacitors. Standard 0805/0603 packages and the like. If you get a small electrolytic capacitor with surface mount leads, or a cylindrical MELF resistor package, they could be inductive.

author: szhighstar
author_rank: Contributor
timestamp: July 01, 2012, 07:10:38 am
content: do you need inductor with low inductance?