Hi folks
I have some PCBs for premaps and amps that use the IRF610 MOSFET, which has an input capacitance of 140pF.
In my parts stash I already have lots of MOSFETS, but no IRF610s.
For instance I have IRF640s but those have 1300pF Ciss, closer are the IRF520s I have at 360pF.
The lowest Ciss parts I have are the IRFR214 at 140pF, the highest are FDD8447L at 1970pF.
I'm not sure how important Ciss is, I have read that the lower Ciss parts have better high frequency response whereas the high Ciss parts have better bass frequency response, is this accurate?
Also, are higher Ciss parts harder to drive, requiring higher Bias currents?
I have some PCBs for premaps and amps that use the IRF610 MOSFET, which has an input capacitance of 140pF.
In my parts stash I already have lots of MOSFETS, but no IRF610s.
For instance I have IRF640s but those have 1300pF Ciss, closer are the IRF520s I have at 360pF.
The lowest Ciss parts I have are the IRFR214 at 140pF, the highest are FDD8447L at 1970pF.
I'm not sure how important Ciss is, I have read that the lower Ciss parts have better high frequency response whereas the high Ciss parts have better bass frequency response, is this accurate?
Also, are higher Ciss parts harder to drive, requiring higher Bias currents?
Very important based on real scheme, used transistor connections and frequency correction.
Leisure fictions.
You give too little information for a clear answer. Depending entirely on the circuit and on what the MOSFET is used for, a MOSFET with higher Ciss could work fine, it could cause oscillations resulting in gross distortion and possible damage to tweeters and output transistors, or anything in between.
Aah, specifics. I have a Bride of Zen which uses two IRF610 and a Pass Labs Headphone Amp that uses four IRF610. I also have a pair of boards labelled Pass AM v1.5 which I take it is Aleph Mini, these use a pair of IRFP240 each.
Use the irfp214. What matters mostly is the reverse capacitance which gets multiplied by the voltage gain and in most cases exceeds that of the input. The input meanwhile acts according the trasconductance , higher it is lower is the input voltage variation, hence lower is the input capacitor's effect . By this the irfp214 is superior .
Thankyou for the info.
The one issue with using those is that they are in the DPAK/TO-252 package. I can solder them to pieces of copper so they can be then bolted to a heatsink, and I think that would be a similar thermal capability to the TO-220 package of the other IRF MOSFETs I have.
I'm only building low power devices so it should work I think.
The one issue with using those is that they are in the DPAK/TO-252 package. I can solder them to pieces of copper so they can be then bolted to a heatsink, and I think that would be a similar thermal capability to the TO-220 package of the other IRF MOSFETs I have.
I'm only building low power devices so it should work I think.
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