How can I combine the two channels of a Waveform generator

[jerryjmcconnell]

Hi

I am taking a self paced course on practical electronics ( Only on the first couple of lessons so I am a total newbie)..the course, for those interested is:

http://www.thegreatcourses.com/courses/understanding-modern-electronics.html and it uses The Art of Electronics 3rd Ed. as a supplementary text book.   

I am trying to duplicate an experiment/exercise using a cap to filter a noisy sine wave.  I don't have all the expensive Agilent gear used on the videos but I have started a modest lab of my own to help facilitate the learning process.

So I do have a Siglent SDG1025 signal generator - I was thinking that on channel 1 I could generate a sine wave and on channel 2 output the built in 'noise' wave form ( there does not appear to be a way to combine them internally on this model)...and somehow feed that combined waveform (hopefully it would appear as a noisy sine wave) into my circuit.

I did search the forum a good bit (still  finding my way around) and saw some similar (but nothing identical) questions. I have a query into Siglent (but, or so I was told,  all the US tech support personnel are in Boston this week, a trade show I guess?) 
 
I am guessing putting a T on each output and cabling them in parallel  - might not be the correct way to do it - but I simply don't know enough to know for sure.  I have yet to start playing with the Siglent waveform generation software that came with the box - I am going to look into building a single noisy waveform - not sure if this is yet possible or not.

In the meantime - if anyone has any suggestions I would be more than happy to listen.

Thanks in advance.

Jerry

[jlmoon]

Hello,

Providing the two waveforms are in phase with one another there are several methods to do this.  A simple one would be to create a simple mixer using 10 k resistors, tying all of them together on one end calling this the output.  Then apply your signals to each flying lead end of each resistor, this is a crude way to pull this off but will probably do what you're needing for your experiments.  Another way is to use op-amps for each signal source and apply the outputs of these into that same resistor combination, although this takes a bit more design and a good understanding of op-amps and how to use them.  If you're interested in the op-amp version look up the EEVBlog video or W2AEW's youtube video #75 on a tutorial on op-amps and how they function. 

[cyr]

http://www.radio-electronics.com/info/rf-technology-design/coupler-combiner-splitter/rf-resistive-splitter-combiner-divider.php

Three resistors (either ~16.6 ohms or ~50 ohms depending on the variant you build), and three BNC connectors...

[jerryjmcconnell]

Thank you for your reply - I'll be starting op-amps soon so maybe I'll postpone that particular approach util I understand them.

I infer from your response that joining the two outputs without some form of protections is not a good idea. So I'll see if I can build a noisy waveform using the supplied software.

Thank you.

[jerryjmcconnell]

Ok - Thank you - another option to consider - seems similar ( but significantly more detail) to the first suggestion of using 10k resistors.

Thanks for that link.