another question about function generator...

[SnakeBite]

in the description of the FG it's says that it's "Synthesized Function Generator" is that mean that it's analog ?
for example the Hp 3325b is it analog or digital FG?

thanks
Idoaricha

[amspire]

I don't think "Synthesized" has to mean Digital, but it does in the case of the 3325B. Definitely digital.

The HP 3325 was a wonderful device, but by today's standards, it is very big, involves a huge number of components, and it had custom output attenuators that had great performance, but were easy to damage and very expensive to repair. No arbitrary waveforms - just sine, square and a few triangular waveforms with modulation available.
 
HP used the word to indicate the waveforms were not generated from a traditional oscillator circuit.

I don't think anyone would use the term much now for Function Generators.

Richard

[SnakeBite]

does arbitrary waveform capability important? don't we use normally only sin ,square and triangular?

[amspire]

does arbitrary waveform capability important? don't we use normally only sin ,square and triangular?

Most people use the standard waveforms most of the time.

However, occasionally the arbitrary waveform is very useful. For example, to simulate a problem, you can capture a waveform on a digital oscilloscope and load the waveform into the generator, and then use the generator to make the waveform that caused the problem.

If you don't know that you need an arbitrary waveform generator, then you don't need it.

Richard

[ejeffrey]

Yeah, I have used many arbitrary waveform generators but never actually used the arbitrary waveform feature.  The rare occasion when I need something other than the standard waveforms I generally find that the AWG is not up to the task and have to use a computerized DAQ card -- for something like very long digital pattern output or weird tone bursts that don't fit in the sample memory of most AWGs.

[saturation]

Today DDS is a popular way to make high quality synthesized waveforms. 

http://en.wikipedia.org/wiki/Direct_digital_synthesizer



In ye old days, people could invent their own, and generically, digital approaches were labeled waveform synthesis or digitally synthesized as they were 'synthetic' rather than as the result of natural electronic phenomena, like oscillations.  Analog FG began with a basic sine wave oscillator and shaped it through various means to get square, triangle, ramp etc.,

[ejeffrey]

Today DDS is a popular way to make high quality synthesized waveforms. 

That is true, but your typical 'DDS function generator' like the aglient 33220A series are pretty much terrible spectrally speaking.

[saturation]

Yes, I don't have 1st hand experience with that arb generator, but generally, spectral purity is the illness of digital synthesis.   OTAH, frequency stability is the illness of analog generators; you can get the best of both in each method, digital or analog, but at high costs. 

Today DDS is a popular way to make high quality synthesized waveforms. 

That is true, but your typical 'DDS function generator' like the aglient 33220A series are pretty much terrible spectrally speaking.

[alm]

That is true, but your typical 'DDS function generator' like the aglient 33220A series are pretty much terrible spectrally speaking.

Compared to an analog function generator or signal generator? Compared to analog function generators they're a lot a better (don't have experience with the 33220A, but do have experience with similar models). But you won't mistake them for an RF signal generator.

[SnakeBite]

what do you think about wavetek 278 FG?? is it good?

what is more important in general use FG - a large signal possibilities (square , ramp , triangle, sin , dc , pulse ,Sawtooth) or signal accuracy/integrity?
i don't know what to decide a have two FG one with more signal (writen above) option but not very accurate but the other has only the basic signals (square , traingle , sin , pulse ,dc) and a lot more signal accuracy/integrity which one is a beter pick?

[saturation]

Its very good, but as mentioned earlier,  its an early form of digital synthesizer and the harmonics of its waveforms are noisier.  Check the spec sheets. 

Precision is better.  Without it you won't know if any instability in your design or testing is due to instability from within the DUT or your test signal.  For general design, different waveshapes are need, but most work today use sine, square and pulse; rather than rely on an analog FG to have various waveforms available through analog waveshaping circuitry [ for rarely used waves like ramp, or sawtooth, popular during analog days], an arb in a DDS like device can make anything you want when you need it.

The Hantek 3x25,  see the thread on eevblog, is a DDS-like generator, but it has rudimentary arb capability, which makes for a versatile generator that rivals analog versions.  Its stability is better than most analog generators, but worse than low cost digital ones.  I've tested its arb capability to 100kHz. Its largest drawback compared to analog generators is its lack of VCO and sweep capability; mechatrommer, marmad and others forum members are trying to improve functionality through hacking the its PC software, you can read the long thread of developments.  Its still for sale from China.

 

what do you think about wavetek 278 FG?? is it good?

what is more important in general use FG - a large signal possibilities (square , ramp , triangle, sin , dc , pulse ,Sawtooth) or signal accuracy/integrity?
i don't know what to decide a have two FG one with more signal (writen above) option but not very accurate but the other has only the basic signals (square , traingle , sin , pulse ,dc) and a lot more signal accuracy/integrity which one is a beter pick?

[nquantum]

i found simply circuit here u may interest:
http://www.overunity.com/6857/diy-simple-signal-generator/

[TerraHertz]

i found simply circuit here u may interest:
http://www.overunity.com/6857/diy-simple-signal-generator/

http://www.overunity.com
Oh, that's a goldmine. Of... ah... entertaining stuff.