What's the application of O ohm resistors?

[oilytong]

Hi,

I would like to ask if there is any use for a 0 Ω resistor besides using it as a jumper of some sort? I found this circuit for a certain device that uses it and just wondering what it may be used for.

I attached the circuit in the word document.

Thanks.

 

[IanP]

Re: O ohm Resistor

Funny things can happen in (very) RF circuits.
It is possible that the 0Ω is used here as a very small inductor...

In non-RF application they have only "jumper" (or sometimes fuse) meaning.

 

[chihhao]

Re: O ohm Resistor

One question.Thanks.

(1)To use 0O or (2) to use solder to be a through way for RF circuit

Which way is better ???

 

[trigger74]

O ohm Resistor

For RF circuit, it is better to use 0 ohm resistor because a solder has many variance...... included inductance, resistance, etc.

And in some products, 0 ohm will be used to replace the EMC components like inductors and capacitors.

 

[biff44]

Re: O ohm Resistor

You did not say what type of component you found this part of the circuit in, so I will have to guess. It looks like this portion of the circuit is some sort of DC bias injector, which provides DC voltage to an active component. In that case, the series 0 ohm resistor would serve one of two purposes:

1) a crude attenuator, where you can leave the value at 0 ohms if you want the maximum power out, and can put in 10 or 20 ohms if you want to drop the output power a dB or two.

2) a stability enhancing resistor for an amplifier output. If the amplifier oscillates with a certain load, adding a 20 or 30 ohm resistor in series with the output might cause the oscillations to cease. Note also a second resistor labelled "NP" (not populated). That 2nd resistor can add some resistance to ground to stabilize an oscillating amplifier (note that the capacitors to ground are an ac short circuit, especially if you replace the 2pF with something larger like 20 pF).

 

[kekon]

Re: O ohm Resistor

0 ohm resistors are widely used in some type of electronic equipment because they are easier to assemble in one-layer pcbs than using short wires (jumpers). In addition they look better For instance, HAMEG company uses one-layer pcb's in some types of their equipment where pcbs are full of such resistors.

 

[knavekid]

O ohm Resistor

Another good use for zero ohm resistors is to be able to isolate part of the circuit for debug purposes. For example, if you need to debug a switching power supply, a zero ohm resistor on the output may be removed to isolate the rest of the board while an external load is attached.

 

[xvibe]

O ohm Resistor

Some circuits use this resistors to make a separation between ground or power planes.

 

[bimbla]

Re: O ohm Resistor

0ohm resistors are used to seperate the return paths of analog, digital, control and power circuits so that they do not share any common path but meet at one single point.
Any autorouter does not have this intelligence. So 0Ohm resistors allows seperate return paths as well as use of autorouters.

bimbla.

 

[toonafishy]

Re: O ohm Resistor

I notice in the catalogs that 0 ohms resistors come in +/- 5% tolerance. Verrry interesting...

 

[oilytong]

Re: O ohm Resistor

Thanks all for your contributions, it has been helpful.

You did not say what type of component you found this part of the circuit in, so I will have to guess. It looks like this portion of the circuit is some sort of DC bias injector, which provides DC voltage to an active component. In that case, the series 0 ohm resistor would serve one of two purposes:

1) a crude attenuator, where you can leave the value at 0 ohms if you want the maximum power out, and can put in 10 or 20 ohms if you want to drop the output power a dB or two.

2) a stability enhancing resistor for an amplifier output. If the amplifier oscillates with a certain load, adding a 20 or 30 ohm resistor in series with the output might cause the oscillations to cease. Note also a second resistor labelled "NP" (not populated). That 2nd resistor can add some resistance to ground to stabilize an oscillating amplifier (note that the capacitors to ground are an ac short circuit, especially if you replace the 2pF with something larger like 20 pF).

Biff44, I got this circuit from a LNA chip RF2472 by RFMD. You mentioned something about the "NP" resistor, what does "not populated" mean? Would any value resistor be suitable?

Thanks.....

 

[biff44]

Re: O ohm Resistor

That is a term we use in the US. If you want some pads on the printed circuit card, but do not initially want the assembler to solder anything to those pads, we often put a resistor of the right chip size on the schematic, but instead of a ohmic value, we say NP, or Not Populated. That way, later on you can add any surface mount part that you might wish of the correct size at that location. It is helpful during development testing, when you are not really sure of what you will need to get an integrated circuit to work properly.

 

[chihhao]

Re: O ohm Resistor

So the conclusion is to use 0 Ohm resistor to be a short circuit is
better than to use solder. ? Can I say that??
Thanks.

 

[springf2000]

Re: O ohm Resistor

according to my experience of the WCDMA power desin:
1)if the output power is high(above 10dBm),y should not use the 0 ohm as the jumper,because the lossy on the 0 ohm is high,then the resistor may became a nonlinear component,it would influence your linearity of your circuit,otherwise you can use it!
2)i f the output power is high and you must use a jumer,the y can move the 2pF capacitor forward to the position of the 0 ohm, the use the resonantor capacitor of your frequency in the position of the 2pF,that shall not influence your feature of your circuit!

in fact ,y can just try,that is a simple way to solve your problem!