EMRFD Message Archive 14334

Message Date From Subject
14334 2017-09-19 08:12:15 ab7vf Curve Tracer

I'm considering building a curve tracer .. What in (anyone's) opinion is a "good" range for the base step
current/ gate step voltages  ..Small signal npn/pnp ..njfet mosfets


14335 2017-09-19 09:52:58 chuck adams Re: Curve Tracer
I use

You can set the steps and ranges and you can save the
data in ASCII to your computer for plotting and analysis.

I use gnuplot to generate curves.  I can come up with some
demos, if you like....

chuck, k7qo

14336 2017-09-19 14:22:44 Mike Re: Curve Tracer

One of the on-line homebrew designs that I think might (at least
partially) meet your needs is the design provided in "Electronics World"
magazine for August 1971. This is available on-line (a google search on
"Electronics World Magazine Archive" should provide a link). This
design provides for base/gate drive steps of 2 uA to 1 mA/step for
bipolars and 0.2 V to 1.0 V/step for JFET's. Although I don't think it
directly addresses testing of MOSFET's. And this design uses 2n1671
unijunction transistors; I think the unijunction transistors could be
replaced with dual bipolar arrangements per Solid State Design for the
Radio Amateur pages 173-174.

I can provide a list of other on-line resources for homebrew curve
tracer designs if desired.

Mike Dinolfo N4MWP

14337 2017-09-19 17:56:23 jim Re: Curve Tracer

Thanks Chuck and Mike for the replies

I've got an op-amp based design (my first semi-original opamp effort) that I've glopped together as a first try .. It works, just trying to decide
how many ranges and values.
I'm mostly hardware hacking and staying away from software solutions
"americanradiohistory.com" has almost all the magazines for perusal and download.
I've found that the ujt based ones are too tweaky for my taste
More to come as the rainy season hits

Thanks again, Jim
14338 2017-09-20 00:21:53 chuck adams Re: Curve Tracer

Good luck on the project.  I got the Peak critter and I really love it. 
I realize it isn't for every one.


chuck, k7qo

14395 2017-10-20 16:14:29 neiperalta Re: Curve Tracer
Is there any missing connection in the Electronics Now schematic?
Where does the emioter current flow to the collector power supply?

73 - LU5DNM
14396 2017-10-20 20:56:28 jim Re: Curve Tracer

14397 2017-10-21 09:11:05 Norberto Modanesi Re: Curve Tracer

Schematic you have mentioned in Electronics World. August 1971


14398 2017-10-21 21:45:15 jim Re: Curve Tracer

14399 2017-10-22 10:22:48 Norberto Modanesi Re: Curve Tracer

Yes. That is.



14400 2017-10-22 16:27:54 Jim Strohm Re: Curve Tracer
Any chance that somebody can post that article to this group's file section along with a corrected schematic?


14401 2017-10-22 18:13:53 K5ESS Re: Curve Tracer
14402 2017-10-22 23:02:08 jim Re: Curve Tracer

14407 2017-10-23 10:00:58 Norberto Modanesi Re: Curve Tracer

I think there is another mistake in the schematic. How the Ib polarity is changed when changing NPN/PNP?



De: emrfd@yahoogroups.com [mailto:emrfd@yahoogroups.com]
Enviado el: domingo, 22 de octubre de 2017 10:14 p.m.
Para: emrfd@yahoogroups.com
Asunto: RE: [emrfd] Curve Tracer



14409 2017-10-23 22:01:21 jim Re: Curve Tracer

14411 2017-10-24 21:56:18 Jim Strohm Re: Curve Tracer
Looks to me like the two unobtainium unijunction transistors serving as relaxation oscillators could be replaced by NE555 or equivalent without too much difficulty.

And ... what were the corrections again?  I haven't really been following this thread carefully.


14414 2017-10-26 00:54:40 gi0gdp Re: Curve Tracer
As a side to this i have a very similar but simpler curve tracer from 1970 something that i built.
It never really had a job until about 1985 when alot of surplus RF devices appeared here and whilst
they often where quoted as "25 watt FM" devices nobody had a clue as to what sort of Vce they had.
Well the tracer sure shows it when at the end of the trace it goes vertical. Best of all calibration was dead
easy you just got say a MRF247 and looked to see the point at the end of the constant current line at which it
went vertical. Because it was all 50 Hz stuff there was no permanent damage.
Basically you could easily distinguish 28v devices from 13.8v ones
14418 2017-10-27 10:49:36 ab7vf Re: Curve Tracer
Hello all

For your amusement/consideration, I posted a circuit diagram for collector ramp/base step generation in folder "curve tracer" based on op-amps
No unobtainum ujt's or that cruft ..I used lm158's cause thats what I had ..lm1458 did not work in the step-generator portion