Dave Dixon
New Member
My buddy and I built a quantity of rather elaborate multistage voltage controlled filters and used Murata 220pF 1% C0G caps in the filter core (follow this link):
https://ca.mouser.com/Search/ProductDetail.aspx?qs=rbJCU8ygG7Chd%2biwiajKKQ==
The filters seemed to be filtering OK, but when driven to the conditions for self-oscillation, they would only oscillate (if at all) above a certain frequency, well into the audio range. Below that frequency, the oscillations would die away very quickly. We reviewed the entire design and found nothing amiss, checked all resistor values, etc, and everything was fine. Finally, we hit on the idea that maybe something was dodgy about the caps. Out of sheer desperation, we replaced them with the same spec caps of another brand. Long story short, the problem is solved, and the filters now work exactly as intended.
We have come to the conclusion that these Murata ceramic caps are seriously defective. Has anyone else had problems with these caps, by any chance?
https://ca.mouser.com/Search/ProductDetail.aspx?qs=rbJCU8ygG7Chd%2biwiajKKQ==
The filters seemed to be filtering OK, but when driven to the conditions for self-oscillation, they would only oscillate (if at all) above a certain frequency, well into the audio range. Below that frequency, the oscillations would die away very quickly. We reviewed the entire design and found nothing amiss, checked all resistor values, etc, and everything was fine. Finally, we hit on the idea that maybe something was dodgy about the caps. Out of sheer desperation, we replaced them with the same spec caps of another brand. Long story short, the problem is solved, and the filters now work exactly as intended.
We have come to the conclusion that these Murata ceramic caps are seriously defective. Has anyone else had problems with these caps, by any chance?