×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Are you an
Engineering professional?
Join Eng-Tips Forums!
• Talk With Other Members
• Be Notified Of Responses
• Keyword Search
Favorite Forums
• Automated Signatures
• Best Of All, It's Free!

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Does anybody know the ESR of a schottky diode?

Does anybody know the ESR of a schottky diode?

(OP)
Hello,

I want to tune a small loop antenna with a SMD schottky diode (1,4 x 0,6 mm). I can´t find any information about the ESR of schottky diodes at 433 Mhz.

0,01Ohm? 1 Ohm? 10 Ohm?

Has anybody a idea about the ESR of small schottky diodes?

Roman

Replies continue below

RE: Does anybody know the ESR of a schottky diode?

Depends on the current. On the Voltage vs. Current curves select an operating current, read the voltage and Re=V/I.

Approximatelly inverselly proportional to the current
until at very high current values the series resistance
dominates.

RE: Does anybody know the ESR of a schottky diode?

Roman,

when you said small you really meant small!

Just to clarify, are you talking about using the schottky diode reverse biased like a varicap, changing the bias to change the capacitance, thereby resonating the loop at 433MHz?

RE: Does anybody know the ESR of a schottky diode?

(OP)
Yes I would use the schottky diode reverse like a varicap.

The smallest mechanical trimmer is quite big (TZR1/Murata: 1,7 x 1,5 mm) and has a high ESR (about 0,5 Ohm). A small microprozessor with InCircuit programming and DA output is on board so it should be easy to change the bias.

I should need a ESR about 0,2 Ohm at 100mA/433Mhz/0...1,8V bias.

Roman

RE: Does anybody know the ESR of a schottky diode?

Roman,
I don’t think you will have much luck with this idea. I checked out the HP/Agilent schottky diodes on the web. They give a linear equivalent model for SPICE and these have resistances of around 8 ohms (for HMPS-282x and HSMS-281x for example). How relevant these models are to the reverse bias situation is not clear, but it is so far above the values you need, I don’t hold out much hope.

I guess the problem is that if you use an uncharacterised parameter like this then it may work on one batch but never work again. Presumably a standard varicap has too much capacitance swing for your application. You could stick a small cap in series with the varicap to reduce the capacitance swing.

RE: Does anybody know the ESR of a schottky diode?

Roman:
If you want to use a diode as VARICAP, you bias it
backwads, i.e. current=0. The resistance depends on the
dielectric loss in series with C and || with the leakage current.

RE: Does anybody know the ESR of a schottky diode?

(OP)
When logbook wrote, I will have about 8 Ohms - that will be much to much. 0,1...0,3 Ohms would be the maximum.

Thank you very much for your answers!!! It was my first time in this forum and I hope that I can help other people as good you did.

Roman

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

• Talk To Other Members
• Notification Of Responses To Questions
• Favorite Forums One Click Access
• Keyword Search Of All Posts, And More...

Register now while it's still free!