Forward Bias voltage drop for a SCHOTTKY BARRIER RECTIFIER - Page 1
Forum section: electronics / projects

author: OutThere
author_rank: Contributor
timestamp: January 21, 2023, 08:42:52 pm
content: it's in a TO220 it is an SBL2040CT in the data sheet it says Forward Voltage drop @ If 10a , so I used the diode test feature of my DVM, should i get the same results , or less

author: TimFox
author_rank: Super Contributor
timestamp: January 21, 2023, 09:04:35 pm
content: No, your DMM cannot possibly source 10 amperes on diode test.Therefore, the voltage drop will be less at the maybe 1 mA test current of the DMM.Note that manufacturers specify themaximumvoltage drop at a specified current: your device will probably be lower than that voltage.

author: magic
author_rank: Super Contributor
timestamp: January 21, 2023, 09:25:44 pm
content: Certainly less, maybe 0.2~0.3V for a power schottky like that, while the 10A spec may be 0.5~1V (guessing).See if there is a plot of forward voltage vs forward current in the "typical characteristics" section of the datasheet, this would give a clue what to expect.

author: bdunham7
author_rank: Super Contributor
timestamp: January 21, 2023, 09:56:11 pm
content: Quote from: OutThere on January 21, 2023, 08:42:52 pmThe 10A Vfspecs are given in the datasheet at a Tjof 25C, which can only be a momentary (pulse) condition. Your Vfas the junction heats up will be less and less. And then if you try to characterize the device at 100C, you'll find that your 1mA or so test current of your DMM will be more in line with the reverse leakage current, not the forward voltage drop.

author: OutThere
author_rank: Contributor
timestamp: January 23, 2023, 02:29:42 am
content: thanks bdunham7 , magic, TimFox, I am getting around 138mV. and reverse polarity OL , so I assume it's good.I have another question i have an N channel MOSFET K2545 N Channel MOSFEThttps://pdf1.alldatasheet.com/datasheet-pdf/view/213104/TOSHIBA/K2545.htmlI tested the MOSFET with the generic testhttps://www.utm.edu/staff/leeb/mostest.htmthe meter stayed at OL Looks like it needs 10v on the gate? do all MOSFET's have a Zener from the Gate to the Source?I have seen electronics parts testers on eBay and Aliexpress, are they good? if so any recommendations

author: TimFox
author_rank: Super Contributor
timestamp: January 23, 2023, 03:41:06 am
content: Almost all power MOSFETs have a Zener diode from gate to source, since it is very easy to destroy the insulated gate structure from an applied charge into the high impedance of an unprotected gate.

author: OutThere
author_rank: Contributor
timestamp: January 23, 2023, 04:30:22 pm
content: so how accurate is the multimeter test for a MOSFET , what is a way to test MOSFETs. I saw your sig. I am retired too. Retired last year. I have an AA in electronics, although around that time computers were starting to be everywhere so I went into the computer field instead, My Mom was also a FORTRAN programmer for NIH. Now retired taking all my 40 years of electronics and computers out of the attic. I have some test equipment with NIXIE tubes and my Tek 465 O'scope. going to get back to making projects and PCBs again and getting my old PC's running have a bunch of old MFM and IDE hard drives.I saved everything