5 ms·

Wouldn't that be pretty easy to do as well? The most crude way to have a DC offset is to just pipe the output through a voltage divider with a potentiometer no?

Wouldn't that be pretty easy to do as well? The most crude way to have a DC offset is to just pipe the output through a voltage divider with a potentiometer no? As for amplitude control, an op amp can be used again with a potentiometer to control the resistors needed for a specific gain right?

jmwilson 7y ago
Sure, the voltage divider works ... if the load impedance is high. Not a good idea for a 50 Ω load. Op amp needs a dual-rail power supply, so it needs some auxiliary power, then power electronics to get both rails. Stuff starts to get complicated, and now that $1500 Keysight box starts to looks worth its price...
- glitchc 7y ago
  This. A function generator is not a trivial piece of digital electronics. It's a complex, highly analog beast, where the digital component of the circuit is actually rather small. Nowadays a dedicated IC (such as the XR2206) is the starting point for a home-made FG. Here's one kit: http://electronics-diy.com/electronic_schematic.php?id=128 http://electronics-diy.com/electronic_schematic.php?id=128
  - cushychicken 7y ago
    I'd even argue that the XR2206 is pretty obsolete when it comes to function generation methodologies. For one thing, it's very limited in frequency - 1MHz max, and dependent on analog components to generate it. For another thing, it's really limited in waveform types. Practically, you can only generate sine, triangle, and square waves. Modulation is possible, but requires extra hardware to pull off. The advantage I see of the DDS is that, once the signal generation portion of the product is software based, you can push upgrades to functionality via software updates. Not something any XR2206 can do!
aDfbrtVt 7y ago
In theory yes. The issue is the different load conditions will mess with the voltage divider bias. Check out page 272 and onward of the HP33120A manual https://coupp-docdb.fnal.gov/cgi-bin/RetrieveFile?docid=206&filename=hp_33120a.pdf&version=1 https://coupp-docdb.fnal.gov/cgi-bin/RetrieveFile?docid=206&...
- jacquesm 7y ago
  Why compare a commercially available top of the line function generator with a hobby project? At this level you can add a couple of simple components and get 95% of the functionality and accuracy of the commercial one for a couple of bucks. Go higher than that and you might as well shell out the money for an army surplus one, but that does not get you what he wanted: an opportunity to tinker and learn.
  - cushychicken 7y ago
    Why compare a commercially available top of the line function generator with a hobby project? Because as soon as you do, you start to realize that you can get quite a ways with commodity hardware. Hence, why I started this project. The research I've done on the frontend of this on what's available in the market suggests to me that there's a niche for something that's a little cheaper, and a little easier to use. I also have a hunch that portability is a nice feature for most folks as well. (Hi Jacques!)
    - jacquesm 7y ago
      There is a whole branch of Chinese manufactured pc peripherals aimed squarely at this space, digital scopes, spectrum analyzers and so on, don't they make a function generator?
      - cushychicken 7y ago
        They do, but the usability leaves something to be desired.
    - 7y ago

jmwilson 7y ago

Sure, the voltage divider works ... if the load impedance is high. Not a good idea for a 50 Ω load. Op amp needs a dual-rail power supply, so it needs some auxiliary power, then power electronics to get both rails. Stuff starts to get complicated, and now that $1500 Keysight box starts to looks worth its price...

glitchc 7y ago
This. A function generator is not a trivial piece of digital electronics. It's a complex, highly analog beast, where the digital component of the circuit is actually rather small. Nowadays a dedicated IC (such as the XR2206) is the starting point for a home-made FG. Here's one kit: http://electronics-diy.com/electronic_schematic.php?id=128 http://electronics-diy.com/electronic_schematic.php?id=128
- cushychicken 7y ago
  I'd even argue that the XR2206 is pretty obsolete when it comes to function generation methodologies. For one thing, it's very limited in frequency - 1MHz max, and dependent on analog components to generate it. For another thing, it's really limited in waveform types. Practically, you can only generate sine, triangle, and square waves. Modulation is possible, but requires extra hardware to pull off. The advantage I see of the DDS is that, once the signal generation portion of the product is software based, you can push upgrades to functionality via software updates. Not something any XR2206 can do!

aDfbrtVt 7y ago

In theory yes. The issue is the different load conditions will mess with the voltage divider bias. Check out page 272 and onward of the HP33120A manual https://coupp-docdb.fnal.gov/cgi-bin/RetrieveFile?docid=206&filename=hp_33120a.pdf&version=1 https://coupp-docdb.fnal.gov/cgi-bin/RetrieveFile?docid=206&...

jacquesm 7y ago
Why compare a commercially available top of the line function generator with a hobby project? At this level you can add a couple of simple components and get 95% of the functionality and accuracy of the commercial one for a couple of bucks. Go higher than that and you might as well shell out the money for an army surplus one, but that does not get you what he wanted: an opportunity to tinker and learn.
- cushychicken 7y ago
  Why compare a commercially available top of the line function generator with a hobby project? Because as soon as you do, you start to realize that you can get quite a ways with commodity hardware. Hence, why I started this project. The research I've done on the frontend of this on what's available in the market suggests to me that there's a niche for something that's a little cheaper, and a little easier to use. I also have a hunch that portability is a nice feature for most folks as well. (Hi Jacques!)
  - jacquesm 7y ago
    There is a whole branch of Chinese manufactured pc peripherals aimed squarely at this space, digital scopes, spectrum analyzers and so on, don't they make a function generator?
    - cushychicken 7y ago
      They do, but the usability leaves something to be desired.
  - 7y ago