How can I produce sinewave using integrator?

[semiconductor]

How can I produce sinewave using Integrator???
frequency range: 0.1Hz -> 200 Hz

Thank you beforehand!

 

[flatulent]

Re: sinewave generator!

The usual way is to have two integrators in a loop. You need some nonlinearity in the feedback around each amp to limit the amplitude so that it is a sine wave and not a square wave.

 

[papyaki]

Re: sinewave generator!

Hi,

Have a look at the inside schematic of the old ICL8038. A non linear network made of transistors is used to generate the sin waveform.

h**p://www.intersil.com/data/FN/FN2864.pdf

* = t

 

[semiconductor]

Re: sinewave generator!

The usual way is to have two integrators in a loop. You need some nonlinearity in the feedback around each amp to limit the amplitude so that it is a sine wave and not a square wave.

Firstly, thank you

Secondly, Can you recommend me some websites that deal with this problem (for further understandings) or can you share some documents related to this problem?

 

[flatulent]

Re: sinewave generator!

If you want a sine wave generator, a better method is to use the wein bridge method which uses only one amplifier. Google has many links like this one http://www.discovercircuits.com/O/o-wein.htm that give practical circuits. Most books on op amps will discuss the two integrator and the wein bridge methods. There should be some op amp books in the ebook section such as

 

[james]

Re: sinewave generator!

The usual way is to have two integrators in a loop. You need some nonlinearity in the feedback around each amp to limit the amplitude so that it is a sine wave and not a square wave.

Firstly, thank you

Secondly, Can you recommend me some websites that deal with this problem (for further understandings) or can you share some documents related to this problem?

Yes, low frequency sinewaves can be generated very easily and with highest purest grade using bridges or integrators.
A while ago I got a pdf on the matter from Texas web. May be it is still there. However as it is very short let attaching here:

 

[geppoilfolle]

Re: sinewave generator!

In theory you find the Wien Bridge oscillator produce the most pure and undistorted Sine Wave.
If this is your goal...

 

[Vitamin-C]

Re: sinewave generator!

Hi,

I have a question for this kind of sinewave generator
using wien bridge:

How precise is this sine wave source ? Is it possible to
create a high SNR (> 80dB) source using this method?

Another question is whether a SNR>80dB sinewave could
be generated by sound card with dynamic range of +/-1V.
Please give me some idea

Vita

 

[semiconductor]

sinewave generator!

Exactly, my teacher want us to design an sinewave generator using integrators, not Wien Bridge. That's why I really need your help.

- If you have any document that present the theory: how integrators cascaded to form a sinewave generator?

- Can you recommend me some reference practical circuit diagrams?

 

[intrepido]

Re: sinewave generator!

We can use 555 with LP filter.

 

[papyaki]

Re: sinewave generator!

Hi,

What you need is a sineshaper. Here are some examples :

h**p://www.geocities.com/SoHo/Museum/4459/circuits/sineshaper.html

h**p://elearning.algonquincollege.com/coursemat/saurioc/ele-2/ELE2-LABS/FUNCTION%20%20GENERATOR%20LAB.pdf

On this one, look at the chapter "Conformateur à diodes" :

h**p://www.alsdesign.fr/alsftp/orcad/Supports_PSpice.pdf

On any case, all these circuits need to have a constant triangle wave amplitude over the full frequency range.

* = t

 

[cesare]

Re: sinewave generator!

You can generate a sine wave using a microprocessor like the MSP430.

The best way is to use a DDS (Direct Digital Synthesis) thecnique so that you can control both phase and frequency of the wave.

Then you need a D/A converter (see SLAA116 on TI website) and a reconstruction filter.

Note that the filter does not need to be tuned on the frequency you are generating because it must suppress Fsampling-Fsine. This allows you to modify frequency.

 

[dainis]

Re: sinewave generator!

Links about DDS project:

/http://www.qsl.net/pa3ckr/signalgenerator/index.html
/http://www.geocities.com/SiliconValley/Code/1835/minidds.html
/http://www.qsl.net/zl1bpu/micro/SIGGEN/Siggen.htm
/http://www.ecdl.hut.fi/~jvan/links.html
/http://www.seattlerobotics.org/encoder/200205/ddsfgen.htm
/http://www.geocities.com/leon_heller/dds.html

 

[geppoilfolle]

Re: sinewave generator!

Hi,

I have a question for this kind of sinewave generator
using wien bridge:

How precise is this sine wave source ? Is it possible to
create a high SNR (> 80dB) source using this method?

Another question is whether a SNR>80dB sinewave could
be generated by sound card with dynamic range of +/-1V.
Please give me some idea

Vita

As i told, the Wien Bridge oscillator produce (ideally) an *absolutely* pure sine wave, whitout distorsion at all.
This is because the phisical principle of functioning of the circuit: the feedback network produce *big* phase-difference for *little* frequency difference on the output, so the circuit go very fast and stay very stable at the *only* frequency for what the produced phase-difference is *zero*.
About the SNR, other problems have to be considered, apart the type of oscillator.
Anyway i'm nearly sure that a *real* 80 dB SNR whit a sound card is pratically impossible, at least whit normal commercial sound cards.

 

[james]

Re: sinewave generator!

As i told, the Wien Bridge oscillator produce (ideally) an *absolutely* pure sine wave, whitout distorsion at all.

Provided that you set gain for Bode frequency precisely and keep it stable with time and with temperature otherwise you will get big distrorsion or damping like waves. An AGC FET based is usually employed.

Sine oscillators with integrators exhibit a larger margin and less criticity than Wien configuration, at expense of purity. In document I uploaded some post above there are some samples of phase shift sine oscillator using integrators, one of them with outputs in quadrature.

 

[metalbeard]

wein bridge oscillator!

Hello:
Am designing an FSK transmitter but in an old fashion way am using two sinewave oscillator (each on dependent frequency
for 1s and 0s) which is wein bridge oscillator with an AGC as shown in the circuit (press on the link below) but the problem is that I couldn't know why is the grounding on the invert input of the op-amp and if it is correct how can I detrmine the gain of this op-amp.
As they are describing in the application note (that I got this circuit from) that the JFET serves as the AGC element, its gate
voltage is zero when the power is applied leading to a low drain-to-source resistance (RDS). This places RG2+RS+RDS in
parallel with RG1, raising the gain to 3.05, and as the output voltage grows, RDS increases, lowering the gain until the
stabilization of the circuit which has the gain of 3
GAIN=(1+RF/( (RG2+RS+RDS)//RG1) ).
So I would be very happy if any one could help me finding the calculations of the gain of this circuit and how they got the
3.05 (assuming that RDS=zero when the power is applied).



http://www.geocities.com/metalbeard/index.html

 

[Tornado]

Re: sinewave generator!

Hi Semiconductor,

Sinewave generator? That brings memories of the past when I needed
a low cost generator I came across an Elektor article in English for a mini function generator, but I cannot find the English.
I have a copy in German but is very clear how it works.

I remember P2 is to adjust the symetry, P4 is to adjust the amplitude, and P3 final output level.
The frequency range is 12Hz to 1KHz and 1KHz to 70KHz.
The clever with this circuit is the diode wave shaper for the sinewave.

In fact I was thinking about that circuit the last few days because I need
a sinewave generator for troubleshooting some circuits at work.

You have to increase the value of C1 to achieve the freq range you are looking for.

Also it has an integrator around N1 just to keep happy you teacher.

I have a suggestion to use a 6volt regulator and operate it from 9Volt
battery.

Regards
Tornado

 

[Tornado]

Re: sinewave generator!

Oops!! there is one more page showing the waveforms, here it is:

Tornado

 

[Borber]

Re: sinewave generator!

Here is a schematics of the sine wave oscillator that uses integrators. Page is extracted from article about THD measuring instrument found on some audio forum searching about audio distortion analyzer.

 

[E-design]

Re: sinewave generator!

Here is a circuit based on the Wien principle as proposed by "Jim Williams" from Linear Tech

Gives very low distortion 3ppm