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MoonWatcher
Bronze Member
USA
98 Posts |
 Posted - 06/26/2008 : 21:01:34
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So I've been bitten BADLY by the mosfets as clippers bug...
The only problem is that the "standard" ones are friggin big, especially with the heatsink on top (over a half an inch tall!).
Does anyone know of some p/n's for smaller mosfets? They don't have to be as tiny as your standard NPN, but something just a touch bigger than one would be perfect. |
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Laurie
Double Platinum Member
Canada
4854 Posts |
Posted - 06/26/2008 : 21:09:32
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quote:
Originally posted by MoonWatcher
So I've been bitten BADLY by the mosfets as clippers bug...
The only problem is that the "standard" ones are friggin big, especially with the heatsink on top (over a half an inch tall!).
Does anyone know of some p/n's for smaller mosfets? They don't have to be as tiny as your standard NPN, but something just a touch bigger than one would be perfect.
G'day! What part numbers are you using now? This will let us think about what a good equivalent might be...
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Dr. Bob
Moderator
Australia
6593 Posts |
Posted - 06/27/2008 : 08:45:27
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Hi Guys
Apologies for jumping the gun.
I'm guessing probably the IRF540 - IRF640 - IRF830 or similar series, seem to be the ones, I commonly used one the net.
Regards Dr. Bob |
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MoonWatcher
Bronze Member
USA
98 Posts |
Posted - 06/27/2008 : 14:44:51
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Sorry for not elaborating.
I've been using the IRF510 OR IRF520 series.
They sound absolutely excellent, IMO.
I know that folks like to pair them with a 1N34A, but there's really no need unless you want to release just a touch more compression.
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MoonWatcher
Bronze Member
USA
98 Posts |
Posted - 07/01/2008 : 04:09:56
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---bump---
Anyone? |
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Laurie
Double Platinum Member
Canada
4854 Posts |
Posted - 07/01/2008 : 04:34:43
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What you are using in an "N channel MOSFET" with a 5.6 Amp current capability. There isn't much that I could find that is like that but smaller... The 2N7000 MOSFET is a candidate - it is 200mA and certainly big enough for clipping in a pedal (Small Bear sell them).
You could also try a J-FET like the standard 2SK30A.
If you try either of these, please let us know how it goes?
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Dr. Bob
Moderator
Australia
6593 Posts |
Posted - 07/01/2008 : 16:52:04
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Hi MoonWatcher, Laurie & Guys
What about the BS170.
Or the VN2222,
both of these are N-Channel Enhancement mode FET's.
I have used the VN2222 in class A circuits, a few times.
Can be slightly tricky to setup correctly, but worth the effort.
Or you could cut off the top, metal tab part of the T0-220 package on the IRF series of MOSFETS, this will make them about half the height.
This is a neat trick to do with the LM780x series regulators, if you are not going to draw a lot of current from them, & it's cheaper than getting LM78L0x TO-92 100mA regulators.
Regards Dr. Bob |
Edited by - Dr. Bob on 07/01/2008 16:56:24 |
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Laurie
Double Platinum Member
Canada
4854 Posts |
Posted - 07/01/2008 : 16:56:16
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MoonWatcher... are you just using two legs of the MOSFET - like a diode? Or are you doing something more sophisticated?
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MoonWatcher
Bronze Member
USA
98 Posts |
Posted - 07/01/2008 : 22:26:11
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I use them as a diode pair shunting to ground, but I tie the gate and drain together as the "cathode."
If you haven't tried it, you owe it to yourself to. I really can't describe it in words.
Next up I'll be throwing them in the feedback loop - this is why it's critical that I find smaller ones.
I might just chop off the tops of the IRF's, because they work so well. I guess it's time to break out the Dremel... |
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Laurie
Double Platinum Member
Canada
4854 Posts |
Posted - 07/02/2008 : 16:43:22
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If you want to stick with MOSFETs, I'd say the 2N7000 is your best bet.
The IRF510 has:
- V-DSS = 100V
- I-D = 5.6A
- R-DS(on) = 0.54 Ohms
- Input capacitance (1MHz) = 180 pF
The 2N7000 is physically smaller and has:
- V-DSS = 60V
- I-D = 0.2A
- R-DS(on) = 1.5 Ohms (approx)
- Input capacitance (1MHz) = 20 pF
Both are MOSFET technology, but are variations on the MOS theme so will sound different because of that.
Additionally, my guess is that the IRF510 will sound warmer because of the higher input capacitance. To be a fair comparison, maybe put a 47pF or 100pF capacitor across the 2N7000s.
Anyway, let us know how it goes if you try them?
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Topic |
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Mosfets that aren't huge?
