SMD components

[dr.power]

Hello guys.

I have an Oscillator circuit made by discrete components (IC's/ Resistors/Capacitors). the capacitors I have used for the circuit are MKT ones (I used MKT caps for the oscillator because they are Stable and have a good temp/voltage change stability) (The frequency stability of the oscillator's ouput is very important for me).
Anyway I want to change the circuit to SMD. I have no experience with SMD componenets. So the question which arises is That I want to know if All SMD resistors and specially SMD capacitors in the bazar are all the same and Stable to be used as oscillator caps? or I have to use an special one?

Thanks

 

[ronv]

They are the same as thru hole ceramic caps and come in X7R and COG. Just harder to read.

 

[dr.power]

They are the same as thru hole ceramic caps and come in X7R and COG. Just harder to read.

Hi and thanks ronv for your reply,

Are you meaning that all of the SMD caps are Ceramic caps? If so can I use them in the oscillator circuits as the oscillators caps?

Thanks

 

[jpanhalt]

SMD caps come in the same varieties as through-hole caps, may be more.

Ceramic are common as are electrolytic in both aluminum and tantalum. Tantalum SMD's will look very much like ceramic ones, but are usually darker color -- often brown, black or yellow. Aluminum electrolytic caps look like through-hole caps but without legs.

John

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[Boncuk]

Using XR5 and XR7 SMD caps they are a bit smaller than electrolytic caps with a narrow tolerance and low temperature drift.

Boncuk

 

[Diver300]

You should use COG components for any capacitors where the capacitance is critical to the frequency stability. They are far more stable than XR5 or XR7.

All the small value capacitors, 100 pF or less, will probably be most easily available in COG anyhow. Large capacitances, over 10 nF or so, have such low impedances at crystal frequencies that if their value changes, it won't affect the crystal frequency significantly.

It is the intermediate values, 100 pF to 10 nF, where you might get a choice of COG or X5R/X7R. That is where you should chose COG for oscillators.