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Re: Is it possible that the 151-0367-00 transistor story is horribly wrong?
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Tom,
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The reference document showing the MPSH05 is Tektronix's own transistor cross reference document. Located right side of the page. However a search of the document also cross references to a A5T3571 AND a SKA6516. So the plot thickens some more. In looking at the A5T3571 The tek xref has this part number specified at 1.2Ghz I was not able to pull a data sheet for a SKA6516 In testing a newer one with out tarnished legs it behaved fine on the curve tracer and I think we have another clue as to the "real part number" given that the curve tracer is well in spec and dialed in I pushed the transistor to mild breakdown. Not to damage but just to when breakdown was starting. The 151-0367-00 that came out of the 457a on the bench currently breaks down right at 25Vdc so that is in line with the A5T3571 data sheet. Which would point to this being a 1.2Ghz part. Zen -----Original Message-----
From: [email protected] <[email protected]> On Behalf Of Tom Lee Sent: Monday, September 18, 2023 10:39 PM To: [email protected] Subject: Re: [TekScopes] Is it possible that the 151-0367-00 transistor story is horribly wrong? Hi Zen, I've seen the MPSH05 mentioned online elsewhere as the part number, but I am dubious. Do you have a Tek reference showing that part number? The 1 Oct. 1986 RPR lists it as something quite different -- SPS8811. The specs of the MPSH05 seem inconsistent with the requirements (e.g., speed) of many circuits using the transistor, so I am guessing that a typo somewhere is responsible for some confusion. That said, component testers are too crude to clear up the situation here. If you have a curve tracer, that's the best way to see what the transistor is doing in all regions of operation. Of course, the reverse region behavior is irrelevant circuit-wise unless there are circuits imposing reverse voltages on the transistor (which there should not be). But as far as understanding why the component testers are getting confused, a curve tracer is the right instrument. Better to look at the raw I-V data, rather than some algorithmic inference from the data. What I predict is that you'll see what I see when I curve-trace microwave transistors: Very low reverse-avalanche voltages. If the component testers ever apply, say, a half-dozen volts or so as they do their search, it is quite probable that they'll break down a microwave transistor in the reverse direction. The ultra-heavily-doped B-E junctions will often show significant conduction with just 3-4 volts in reverse, so an "upside-down" NPN will start to conduct at just a VBE above that. And if the transistor avalanches, then the voltage between collector and emitter could snap to a fraction of the initiating voltage and fool the component tester into thinking that a C-E diode just turned on. As for the DMM6500 result, I've never used that instrument, but I note that the current source in the diode test mode has a compliance spanning at least a 12V range, which can be enough to trigger reverse avalanche breakdown in microwave transistors. If you have a cheapo DMM, try using its diode test function and see if you still see a C-E diode. Most cheap DMMs impose a 2-3V maximum in diode test mode. The MPSH05 shouldn't show this behavior, given the datasheet numbers. -- Cheers Tom -- Prof. Thomas H. Lee Allen Ctr., Rm. 205 420 Via Palou Mall Stanford University Stanford, CA 94305-4070 On 9/18/2023 11:47 AM, Zentronics42@... wrote: I did a little more digging in that lab today. I have a 475A late serial number on the bench and the 151-0367-00 transistors were not tarnished on the legs. I dug up a data sheet and found that the transistor is a MPSH05 This is speced to have the following: |
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