Matching transistors - Measuring hfe

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#61
Hi wds,
As it stands right now, the CT100 is a lot of bang for the buck
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I agree with you on that. I am very tempted to pick one up right now.
We will also approach any new designs so that an external power supply will be possible using the same USB board, thus extending the overall power capabilites. It is our intention to create a cost-effective solution for many engineers and DIY'ers.
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That would be cool.
When do you expect the new version out? I am really interested as I do a lot of device matching. This would really help with power transistors and power FET's. I would clamp the DUT on a heatsink for the test, that should be a consideration. The purchaser could then provide their own heatsink and possibly do four parts at a time.

-Chris
 
#62
anatech said:

When do you expect the new version out? I am really interested as I do a lot of device matching. This would really help with power transistors and power FET's. I would clamp the DUT on a heatsink for the test, that should be a consideration. The purchaser could then provide their own heatsink and possibly do four parts at a time.

-Chris
Click to expand...

A new version will be several weeks away. We have just begun prototyping and testing various parts of the circuits....and only the USB powered side of it. How much overall power will be available when using a wall-wart power suppy will be a decision as we progress with the new project. The multi-test add-on module will also be a serious consideration in the evolution of the design.
 
#64
We haven't decided on how high is high, but something approaching 1A has been discussed. It was not part of our business plan to be a player in the curve tracer market. A niche is good enough for us right now, and I think we have one with a USB only model. There are some quality machines already available and demand must be able to support a design/build venture, or be part of a larger diversity of products.
 
#65
wds said:
We haven't decided on how high is high,
but something approaching 1A has been discussed.
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Just a side note here.
I have both Firewire IEEE1394 and USB 2.0.
Most with not too old PC would have it, too.

FireWire can connect together up to 63 peripherals in an acyclic network structure.

t is designed to support plug-and-play and hot swapping.

Its six-wire cable is not only more convenient than SCSI cables
but can supply up to 45 watts of power per port,
allowing moderate-consumption devices to operate without a separate power cord.

FireWire 400 can transfer data 400 Mbit/s data rates (actually 98.304, 196.608, or 393.216 Mbit/s, but commonly referred to as S100, S200, and S400).

Cable length is limited to 4.5 metres but up to 16 cables can be daisy-chained yielding a total length of 72 meters under the specification.

FireWire 800 was introduced by Apple in 2003,
allows an increase to 786.432 Mbit/s with backwards compatibility to the slower rates and 6-pin connectors of FireWire 400.
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So, Firewire can support considerable power for many devices,
when often using USB you have to add a separate supply.

I know this, as I am to buy an external harddrive for backup.
I will buy such a model that takes like 500GB and supports BOTH USB and Firewire connection.

😕 A question:
How can I know if I have Firewire 400 or Firewire 800 in my Windows XP Home???
I have tried to find this in 'System Info'.
But I haven't found out what Firewire speed I have ...

1394 Net Adapter
Ethernet 802.3
1394 Net Adapter
V1394\NIC1394\69383C10DC00
NIC1394
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If I am right in my guessing,
the Ethernet 802.3 tells I have Firewire 800

lineup
 
#66
45 watts is impressive!...that's nearly 10% of my PC power supply rating. Even at 12V from a larger PC power supply that represents almost 4A. I've known about FireWire speed capabilities for some time, but was unaware that so much power was available. Is that allowable for a single FireWire device, or the aggregate?

I will investigate this further. Thanks for the info.
 
#67
Hi wds,
Now that's good news. Keep up the good work.

When thinking external power, I understand going with a wall wart. Please consider higher levels of voltage and / or current from a supply you are not responsible for.

I was also thinking about a breakout so that "we" could implement an amplifier and divider that would extend your ranges. That way we could go for tube HV or bipolar high power. I guess over current sensing might be an issue for an external unit. You would be supplying test signals and reading a scaled down reading. Your current protection would not be active in that case.

Any thoughts?

Also, consider your unit a good building block with add-ons. You would have a great modular system that is semi customizable. You would not really be competing in that case.

-Chris
 
#73
I wanted to offer a comment here having worked in the semiconductor business. We call the variation from one batch of parts to the next process variation, and while there can be a large variation from batch to batch, there is virtually no variation on a particular wafer. Parts are made in large quantities on wafers. Parts coming from the same wafer should be virtually clones of one another. Those that do not usually have fairly large variation. If you purchase the parts in one lot, there is a fairly good chance that many of them will be from the same lot and perhaps wafer. This is where you'll find an excellent match.

This should be kept in mind when drawing conclusions about a semi manufacurer. If you get a batch that have excellent match it is possible that they're from the same wafer and you cannot draw conclusions about the process variation. Randomly selected parts will not match as well.

In VLSI digital design we verify timing over process, supply voltage, and temperature limits however, we assume no variation on a particular die, since they are all the same within reason.

I should probably add that I did not work on the fabrication side, but these were the considerations working on the design side.

Pete B.


TomWaits said:
I received 100 pcs each of On Semi MPSA42 & MPSA92. I measured the hfe of the devices using a Mastech MS8230B. I also had some older National Semi MPSA42’s so I tested them too. I’m not certain of the exact circuit this digital meter uses internally for this test but here are the results. My obvious purpose was to match NPN and PNP pairs but the results were not as good as I expected.

I am very interested in hearing your comments as this is the first time I have done this type of measurement.

Cheers,

Shawn.

On Semi MPSA92 PNP

hfe - QTY
120 - 2
118 - 3
117 - 5
116 - 5
115 - 2
114 - 3
112 - 9
111 - 11
110 - 8
109 - 24
108 - 13
107 - 12
105 - 2

On Semi MPSA42 NPN
Hfe - QTY
101 - 5
97 - 6
95 - 13
94 - 2
93 - 12
92 - 17
91 - 7
90 - 5
89 - 12
87 - 6
85 - 4
65 - 2
64 - 1
53 - 2
48 - 1
47 - 1
46 - 1
38 - 1
35 - 1

National Semi MPSA42
hfe - QTY
274 - 1
252 - 1
246 - 1
226 - 1
129 - 1
114 - 1
97 - 1
87 - 1
85 - 1
74 - 1
57 - 1
56 - 1
50 - 1
47 - 1
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#75
Re: Re: Matching transistors - Measuring hfe

PB2 said:
I wanted to offer a comment here having worked in the semiconductor business.

We call the variation from one batch of parts to the next process variation, and while there can be a large variation from batch to batch, there is virtually no variation on a particular wafer.

Parts are made in large quantities on wafers.
Parts coming from the same wafer should be virtually clones of one another.
Those that do not usually have fairly large variation.

If you purchase the parts in one lot, there is a fairly good chance that many of them will be from the same lot and perhaps wafer. This is where you'll find an excellent match.

Pete B.
Click to expand...


🙂 Thanks Pete B.
🙂 Even if I have not worked in the semiconductor industry
🙂 my message already in Post #9 is practically identical:


lineup said:

Now also when matching NPN to NPN in a pair
you may end up with different HFE in these 2 transistors,
if you have matched for Vbe.
--------------------

This can happen especially if your transistors are NOT from same BATCH.
This is why it is good to buy for example 100 small signal transistors
in one package, and so try to make sure,
they were made from the same silicon substrate
on the same day and by the same machine!

What will determine the quality of a transistor
is the quality and pureness of the raw material used.
Like with diamond and pearls ... there can be imperfections in the pearl.
Same with the silicon mineral sheets that are used for semiconductors.

When you order you can even ask if you can get all your BC550C from the same original package.
If your supplier can do this, it is good.

Of course this goes for Power Devices, too.
There is a better chance they have similar parameters
if they come from same production unit in a specific day.


Buying a few transistors here and a few there and in different years/months
and maybe even from different brands, manufacturers,
will make it more different to find 2 good matching BC550C.


Regards
lineup
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#76
Hi all

...and this is why matching complementary pairs can sometimes be troublesome. They can never come from the same wafer!

but maybe the newer devices are better matched these days because the process is better tuned to the typical.

MJL3281A gain 75 ...150 = 2:1
2N3055 gain 20...70 = 3.5:1


cheers
John
 
#78
Re: Re: Matching transistors - Measuring hfe

PB2 said:
I wanted to offer a comment here having worked in the semiconductor business. We call the variation from one batch of parts to the next process variation, and while there can be a large variation from batch to batch, there is virtually no variation
Click to expand...


Back in the bad old days -- when most semiconductor memory was made in the U.S. (yes it is true, before the Apple 2+ most of those 4k RAMS were made here) -- you had a lot of variation on a wafer. In those days of yore, when men were men and wore pocket protectors to prove it, semiconductor test was actually a business up in Massachusetts!
 
#79
wds said:
I read a little further about FireWire power and it's current limited to 1.5A from 8V to 30V to a max of 45W (30V * 1.5A). That's still impressive and worth considering. Now on to figure out what voltage my Dell laptop is producing on my 4-wire 1394 port....
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Careful here - many laptops either limit or do not supply power at all to the 1394 port. Check the individual specs on a tower system as well since the amount of power available varies widely model to model and manufacturer to manufacturer.

1394 cables are available in a version that supports an external power supply. And if you have to do that, then you might as well go USB since the bandwidth demands of the curve tracer won't require 1394.
 
#80
Quote from thanh post#41 (page 5)
To me, it's easier to have a low distortion amp with symmetrical topology than asym-topology
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thanh

I am afraid that harmonic distortion measurements can not reveal this audible degradation that I am referring to in my post#36 (page 4)
I hypothesize that due to the asymmetry of all these signals, a pre or power amplifier featuring a complementary (N+P) symmetric topology may show an audible degradation just because (*) of the subject discussed in this thread (dynamic mismatch of “complementary” N+P pairs).
Click to expand...

May be an (ideal) input-output comparator is an appropriate tool for monitoring this

Regards
George
 
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