Identifying 0603 part

[ZiggyStardust]

Hello everyone,

I´m trying to identify a 0603 component inside a power supply circuit. It looks like a simple 0603 two terminal capacitor.

In DC, it works like a 100 kOhms resistor.
In AC, it works like a low pass filter, with 500 kHz BW aprox.

It looks like a ferrite bead but with high DC resistance, but I cannot find one with such a high resistance. Any ideas?

Thanks in advance!

 

[KlausST]

Hi,

0603 is a component with two connections.

I wonder how a "two connections component" can act as a low passfilter with 500kHz bandwidth.

Btw: No, I don´t know any device with such a behaviour.
Where did you find it? Which circuit? What other comonents connected?

Klaus

 

[ZiggyStardust]

Hi,

0603 is a component with two connections.

I wonder how a "two connections component" can act as a low passfilter with 500kHz bandwidth.

Klaus

Hello KlausST,

I connected a series resistor to this component and connected them to a signal generator. Measuring voltage in the series resistor I saw a LPF like behaviour...

I measured it with an LCR meter and this is what I obtained:

R = 100 kOhms
C = 10 pF @ 10 kHz
L = 80mH @ 10 kHz

I found it connected in series with the base resistor of a NPN transistor in the feedback area of a SMPS. This transistor seems to work as some kind of disable signal, it sets feedback voltage to zero when active. Hope this can help...

Thanks for your help.

 

[betwixt]

It is probably just a 100K resistor. It sounds like a reasonable value to be in the base of a transistor. Measuring any single component with a signal generator without taking into account the load on it is pointless. Double check the resistance by reversing the meter probes but my guess is it is just an ordinary resistor. 80mH would be FAR bigger than 0603 size and measuring 10pF barely takes into account the probes themselves and if anything is the surrounding tracks and components.

Brian.

 

[KlausST]

Hi,

L = 80mH @ 10 kHz

Unbelievable. This is a huge value for a 0603 device. Did you cross check your measurement?

Klaus

 

[FvM]

I measured it with an LCR meter and this is what I obtained:

R = 100 kOhms
C = 10 pF @ 10 kHz
L = 80mH @ 10 kHz

Doesn't make sense. If not purely resistive, the impedance at 10 kHz can be either capacitive or inductive, not both. I guess a misunderstanding in operating the instrument.