Using IRFZ44 in place of a IRFP044 - diyAudio
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Old 13th July 2002, 09:01 AM   #1
Nicwix is offline Nicwix  Australia
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Default Using IRFZ44 in place of a IRFP044

I can obtain the IRFZ44 for A$3.00 (possibly less in quantity) whereas the IRFP044 is $7.85 in small quantities.

The IRFZ44 seems to be pretty much the same device in a better package TO-247 instead of TO220.

Key spec.s are as follows:

IRFP044 / IRFZ44

VDSS = 60V (same)
RDS(on) = 0.28 (same)
ID = 57 / 50A
Power Dis. 180 / 150W
Thermal Res. - Case to Sink: 0.24 / 0.5 C/W
gfs: 17 / 15S
td(on): 19 / 14ns
td(off): 55 / 45ns
Ciss: 2500 / 1900pF

Any views on this and are there any other critical specifications to consider?

Nix
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Old 13th July 2002, 09:12 AM   #2
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Prise IRFP044
1.35 euro
in http://www.reichelt.de/
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Old 13th July 2002, 11:33 AM   #3
Warp Engineer
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Use the IRFP044's... You'll probably find it works out cheaper to import these devices from arrow or digikey in america.
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Old 13th July 2002, 11:51 PM   #4
Nicwix is offline Nicwix  Australia
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Minor correction to above

"The IRFZ44 seems to be pretty much the same device in a better package TO-247 instead of TO220."

should read:

"The IRFZ44 seems to be pretty much the same device except that the IRFP044 has a better package (TO-247) and hence higher power rating than the IRFZ44 (TO220 package). OTOH the IRFZ44 is slightly faster."

I appreciate the advice above - but can anyone tell me why the IRFP044 is preferred (given the power of either is ample) - what other specs are important when choosing a MOSFET?

Nix
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Old 14th July 2002, 04:55 AM   #5
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VDSS = 60V .... rail to rail voltage should be less than this
RDS(on) = 0.28 (same) .... meaningless when building analogue amplifiers
ID = 57 / 50A .... high is better
Power Dis. 180 / 150W .... this is a function of die size and hence also Ciss as well as package type .... for a given power rating for the amp output stage we try to minimize total culmative Ciss
Thermal Res. - Case to Sink: 0.24 / 0.5 C/W .... you'll be able to run the bias high with the 044's for a given Junction temp
gfs: 17 / 15S .... higher transconductance is preferred
td(on): 19 / 14ns .... Assuming we set the XA to 50% and operate it below cutoff which is what we normally do then the mosfets dont turn on or off at any time during the waveform.
td(off): 55 / 45ns .... same as for td(on)
Ciss: 2500 / 1900pF .... determines the number of devices that can be placed in parallelled for a given high frequency rolloff.

Hope all that helps.
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Old 18th July 2002, 11:16 PM   #6
Nicwix is offline Nicwix  Australia
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AudioFreak

Thanks for the detailed reply - I understand all your points.

What other specs are important?

I also emailed you re your matched IRFP240 sale.

Nic
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Old 18th July 2002, 11:31 PM   #7
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I haven't tried the Z44, so I couldn't say, but the
higher transcondctance and current rating is going to
make for a slightly different sound. Like the IRF150 or
250, it will probably tend to have better performance
on the bottom, but may be a bit darker on the top.

You might like this better, maybe not. Try it.
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