I dont know enough about parts interchangeability. I followed the link in the C2CE King of Nothing build docs, ordered what I thought were IRF740's and received BS170's in a baggie marked as IRF740. They look completely different. Not sure what to do at this point, other than reorder from somewhere else if these parts are not interchangeable...
King of Nothing: Ordered IRF740 from Tayda, received BS170
- Thread starter fuzz
- Start date
I wrote an e-mail, but I just found out about the error. Just wondering if it's an interchangeable part or if I should source elsewhere in the meantime...Based on cursory research it doesn't look to be an interchangeable part, at least in terms of the voltage this particular pedal produces...
Brett
Well-known member
They’re not. You’re going to need the correct part in this application.
Feral Feline
Well-known member
Tayda has datasheets for both; each product's page has a link to the datasheet:
Get the datasheets and compare details, such as but not limited to the following:
Get the datasheets and compare details, such as but not limited to the following:
| IRF740 | BS170 | |
| VGS | 2v–4v | 0.8v–3v |
| IDSS | 25µA | 0.5µA |
| IGSS | 100nA | 10nA |
| GFS | 5.8S | 320mS |
| RDS | 0.55Ω | 5Ω |
Feral Feline
Well-known member
Further to my post above, I'd like to add that I'm still trying to figure out how to effectively read data-sheets myself.
While I can't explain the items in the far left column above off the top of my head, without looking up what they mean, I can still see the numbers don't even come close to matching.
If you look at diodes 1N914 and 1N4148 datasheets, for a good example of compatibility, you'll find they're basically bang on in spec:
They're identical, why don't the two diodes share the same name? Some further sleuthing online reveals :
When I'm in doubt, I ask the great oracle — typing into an Internet Search Engine such as Google what alternatives are available for a J201, for example, gets back:
J113 and PN4393 are both pin compatible with a J201.
The J113 doesn't have as much gain as the J201, though, I've read.
Another JFET, 2N5457 is often given as a compatible replacement for the J201, and while it has more gain than a J113, it still hasn't quite got the oomph of the J201, IIRC.
For more on JFETs, read the thoughts of those with far superior knowledge than I:
forum.pedalpcb.com
forum.pedalpcb.com
forum.pedalpcb.com
So, asking the oracle if IRF740 is compatible with BS170 and the first and only hit that mentions the two of them together is this thread.
That's a pretty good indication to me that they are not mutually compatible.
While I can't explain the items in the far left column above off the top of my head, without looking up what they mean, I can still see the numbers don't even come close to matching.
If you look at diodes 1N914 and 1N4148 datasheets, for a good example of compatibility, you'll find they're basically bang on in spec:
| 1N914 Fairchild | 1N4148 Vishay | |
| VR Breakdown Voltage | 100v (IR=100µA) | 100v (IR=100µA) |
| VF Forward Voltage | 1v (IF=10mA) | 1v (IF=10mA) |
| IR Reverse Leakage | 0.025µA (VR=20v) | 25nA (VR=20v) . . . [ 25nA = .025µA] |
| CT Total Capacitance | 4pF | 4pF |
| trr Reverse Recovery Time | 4ns | 4ns |
They're identical, why don't the two diodes share the same name? Some further sleuthing online reveals :
When I'm in doubt, I ask the great oracle — typing into an Internet Search Engine such as Google what alternatives are available for a J201, for example, gets back:
J113 and PN4393 are both pin compatible with a J201.
The J113 doesn't have as much gain as the J201, though, I've read.
Another JFET, 2N5457 is often given as a compatible replacement for the J201, and while it has more gain than a J113, it still hasn't quite got the oomph of the J201, IIRC.
For more on JFETs, read the thoughts of those with far superior knowledge than I:
J201 substitute? Oh no, not again...
Question: what's the J201 substitute for ....? Is there a J201 substitute? Answer: it depends :) I'd like to share my point of view for a J201 replacements, using Son of Ben an an example. So we're using JFET for amplifying signal (gain stage). But before I start with measurements, ltspice...
forum.pedalpcb.com
JFET Shootout
Here's a comparison of most of the JFETs we use in pedal circuits. I pulled 5 samples each of 15 different part numbers. I measured Vgs,off and Idss. From that, I used the JFET formula to calculate the Vgs and gm (transconductance) at Id = 200μA. I chose 200μA because that's a typical drain...
forum.pedalpcb.com
JFET Biasing - part 1
I spent a fair amount of time trying to make this as concise and readable as I could. Intro In theory, setting the bias on JFETs should be easy. In practice, not so much. Here are the details on why that is and what we can do about it. Let's review some theory and get the math out of the...
forum.pedalpcb.com
So, asking the oracle if IRF740 is compatible with BS170 and the first and only hit that mentions the two of them together is this thread.
That's a pretty good indication to me that they are not mutually compatible.