A capacitor charging or discharging by a resistor makes an exponential curve.
If you want straight ramps then a constant-current source and constant-current sink circuit must be used instead of a resistor, or an opamp integrator circuit must be used.

 

Hi Audioguru,
Thanks for your reply.
I have been tried that option for my ckt, but i haven't succeded. Signal is degrading for every pulse as shown. It's not showing any sign of envelope pulse. And also As I asked in my previous post, is there any possibility for adjusting rise time ans fall time of puses. Any ideas ?

 

Get rid of your rise and fall pots and their capacitor.
A square-wave is converted to a trapezoid with equal rise and fall times with an integrator. The values of the resistor and capacitor in the integrator determines the rise and fall times.

EDIT:
Your opamp is not powered. Depending on how it is powered and whether the input square-wave has a DC voltage then the opamp might need an input reference voltage.

 

Get rid of your rise and fall pots and their capacitor.
A square-wave is converted to a trapezoid with equal rise and fall times with an integrator. The values of the resistor and capacitor in the integrator determines the rise and fall times.

Hi Audio guru,
I tried , as you suggested but still no sign of propersignal.

EDIT:
Your opamp is not powered. Depending on how it is powered and whether the input square-wave has a DC voltage then the opamp might need an input reference voltage .

I agree, I tried with LM124 opamp. still same output as I posted in previous posts.

In mean time I searched for proper sine wave oscillator, I found but it's giving more offset voltage in real time appliation compare to simulator. How can I get ridoff the offset voltage in this case. Here is the link for sine wave oscillator http://www3.telus.net/chemelec/Projects/Sine/Sine-Osc-1.png

Ibuilt it using LM124. I also tried with LM358, but still same result. Suggest me.

 

There are three parts to what you are trying to achieve.

1) A sine wave oscillator
2) A voltage (or current) controlled amplifier (VCA)
3) An envelope generator, to generate variable rise and fall control signals for the VCA

You have come up with versions of the oscillator, AudioGuru has advised on how to approach the envelope generator, but there seems to be no sign of a VCA so far.
Trying to change the oscillator amplitude level smoothly,over a range of times, using the output of the envelope generator without a VCA is going to be difficult - if possible at all.

You might like to look at the spec sheets of devices like CA3080, LM13700, or SA571 for ideas on VCAs.

 

An LM124 and LM358 are some of the worst opamps ever made.
They have terrible performance above only 2kHz and have high crossover distortion.
Use a TL072 dual opamp instead. Its minimum supply is 7V.

The two zener diodes limit the output amplitude and cause an offset voltage if their voltages are not exactly the same. They cause severe distortion.

I made a low distortion Wein Bridge and a low distortion phase-shift oscillator.
The Wein-bridge oscillator uses a low distortion Jfet attenuator to limit its output amplitude and the phase-shift oscillator uses back-to-back LEDs to slightly clip the signal then it is filtered 3 times with the lowpass phase-shift parts into a good sine-wave.

 

Hello,

You will find all the schematics for the parts rogs mentioned on this page :
http://www.musicfromouterspace.com/analogsynth.php?page=ANALOG

Greetings,
Bertus

 

There are three parts to what you are trying to achieve.
AudioGuru has advised on how to approach the envelope generator, but there seems to be no sign of a VCA so far.
Trying to change the oscillator amplitude level smoothly,over a range of times, using the output of the envelope generator without a VCA is going to be difficult - if possible at all.

You might like to look at the spec sheets of devices like CA3080, LM13700, or SA571 for ideas on VCAs.

Hi Rogs, Thanks for comments.
As audio guru adviced, I tried different values of res ans cap values for my circuit(50Hz), signal rise is seems queit good but I am not getting signal fall proper envelope shape.File attached.

About VCA , Do you mean to I tried for CA3080 ,but there are not in production now a days, I will try to get LM13700. You suggested this for Amplitude modualtion(to combine sinewave and envelope singals.) I tried MC1496 (ckt and PDF attached)amplitude modulator circuit, but I am not getting. as I expected..dont understand why?

As you mentioned, I am working on sinewave oscillator and envelope datector, and also amplitude modulator(VCA)?

 

An LM124 and LM358 are some of the worst opamps ever made.
They have terrible performance above only 2kHz and have high crossover distortion.
Use a TL072 dual opamp instead. Its minimum supply is 7V..

Ok, thankyou for suggestion, I will buy some TL072 OPs

The two zener diodes limit the output amplitude and cause an offset voltage if their voltages are not exactly the same. They cause severe distortion..

Thanks for detailed information....

I made a low distortion Wein Bridge and a low distortion phase-shift oscillator.
The Wein-bridge oscillator uses a low distortion Jfet attenuator to limit its output amplitude and the phase-shift oscillator uses back-to-back LEDs to slightly clip the signal then it is filtered 3 times with the lowpass phase-shift parts into a good sine-wave.

Interesting.... some more explaination please .. because I tried diffrent Wein bridge oscillators(with fand without non linear filaments ckts as datasheets shoowed ..) but I haven't succede,, this was mention in my previous posts... It would be greatful.. if you educate me in this.. Thank you for your help in this project.

 

Hello,

You will find all the schematics for the parts rogs mentioned on this page :
http://www.musicfromouterspace.com/analogsynth.php?page=ANALOG

Greetings,
Bertus

Thank you bertus.. I will try

 

Your simulated circuit picture is too fuzzy for me to see. It looks like you saved it as a fuzzy JPG file type than changed it to a PNG but it is already a fuzzy image as a JPG so changing it does not help. Save it as a very clear PNG file type instead.

The integrating opamp should make an absolutely straight rise-time and an absolutely straight fall-time. The rise and fall times should be exactly the same. A 741 opamp is too slow to make a good ramp above 1khz.

 

The integrating opamp should make an absolutely straight rise-time and an absolutely straight fall-time. The rise and fall times should be exactly the same. A 741 opamp is too slow to make a good ramp above 1khz.

I uploaded .PNG format .. It might be clear now.. and I am using 741 opamp for less than 1Khz freq.

Here I a mtrying to achieve envelope signal.. slow rise and slow decay....as I requested in previous posts.. file attached.

The integrating opamp should make an absolutely straight rise-time and an absolutely straight fall-time. .

you mean like trepizoidal..wave or sawtooth ...

 

I think you are making this more complex than it needs to be. You can achieve what you need to do with just a couple of devices.
I've attached a sketch of the sort of thing I mean.
I'm not at my workbench right now, but if you're intererted in this kind of approach, I can try and breadboard something next week to get some component values. What kind of frequency range is the triangle wave going to operate over, for example?

I'm afraid I don't have any experience with these 'sim' packages -more an old fashioned 'lets actually build it and see if it works' kind of guy, so I don't know how you'd approach simulating this circuit. Maybe someone else could help there?

 

I uploaded .PNG format .. It might be clear now.

Thank-you. It is much clearer now and is a much smaller file size.
Your integrator uses a 2.2k input resistor and only 470pF for its capacitor so its rise and fall times are only 1us which is much too short and impossible for an old 741 opamp to follow. Maybe the capacitor value should be 470nf which is 0.47uF.

 

Thank-you. It is much clearer now and is a much smaller file size.
Your integrator uses a 2.2k input resistor and only 470pF for its capacitor so its rise and fall times are only 1us which is much too short and impossible for an old 741 opamp to follow. Maybe the capacitor value should be 470nf which is 0.47uF.

Hi audio guru, Thank you for comments.. I tried with 0.47uF, but no sign of wave form.. it settle down @-3.5V no rise and fall .. I don't understand....suggestme?

 

I think you are making this more complex than it needs to be. You can achieve what you need to do with just a couple of devices.
I've attached a sketch of the sort of thing I mean.
I'm not at my workbench right now, but if you're intererted in this kind of approach, I can try and breadboard something next week to get some component values. What kind of frequency range is the triangle wave going to operate over, for example?

I'm afraid I don't have any experience with these 'sim' packages -more an old fashioned 'lets actually build it and see if it works' kind of guy, so I don't know how you'd approach simulating this circuit. Maybe someone else could help there?

Hi ROGS, Thank you for your help , Yes Iagree... I am complicating this.. It would greatful.. if you suggest me in clear path....

 

OK, I'll try and put some detail on the circuit early next week, when I have a spare couple of minutes in the workshop.

I'm still not exactly sure what you're trying to achieve -am I right in thinking that you want to modulate your 600Hz with a 20mS (50Hz) triangle wave?

That would look like the attached plot, and would sound like this:

http://homepage.ntlworld.com/roger.shore/600Hz 50Hz triangle mod.mp3


(Short sample length only - import into an audio editor like Audacity (free) to loop the replay)

Is that what you're after?

 

OK,am I right in thinking that you want to modulate your 600Hz with a 20mS (50Hz) triangle wave?
Is that what you're after?

Yeas I am after that.. but small change not Traingle wave.. it is like square wave signal, slow rise and slow fall... pllease check attached file.

Thank you...in advance..

 

I think we're at crossed purposes here! The circuit I've drawn will produce a waveform like the sample I posted. Complete on/off modualation with the triangle wave. Not what you're looking for.

What you are looking for is more like the picture in your very first post -except that it's not to scale!
You need to realise that modulating a 600Hz sine wave with a 50Hz, 50% duty cycle square wave (OK, a modified square wave) will produce tone bursts of only 6 cycles of the 600Hz waveform. Lets allow 1 cycle for rise time, and one cycle for fall time. That leaves a tone burst of 4 cycles! It really isn't going to matter whether the rise and fall times are linear or exponential --you won't hear any difference.

What you will get will look like the attached waveform , and sound like this:

http://homepage.ntlworld.com/roger.shore/600Hz 50Hz sq mod.mp3

If that is what you want, then I suggest you have another look at my circuit attached to post #12 of this thread. A 5%THD sine wave is going to be more than adequate for a 6 cycle tone burst!

Using a VCA and envelope generator to control two individual cycles of a 6 cycle burst is really overkill, IMHO.
Plus the fact that my SA571 modulation waveform would give you a triangle, not the modified square you are looking for.

I'm still not sure exactly what you are trying to achieve. It sort of sounds like you're trying to copy telephone tones. If that is the case, there are better ways of doing that than this way!!

 

You need to realise that modulating a 600Hz sine wave with a 50% duty cycle square wave (OK, a modified square wave) will produce tone bursts of only 6 cycles of the 600Hz waveform. Lets allow 1 cycle for rise time, and one cycle for fall time. That leaves a tone burst of 4 cycles! It really isn't going to matter whether the rise and fall times are linear or exponential --you won't hear any difference.
!!

hI ROGS, Thankyou for details....
Yes , absolutly... I am looking for 50% duty cycle, As I posted in my previous posts, when ever I switch on my sqaure wave goes to upto 5V, off 0V again. when pulse goto 5V my sine must follow.. sqaure wave pulse.. (chnging the amplitude.) and settle down at 5V amplitude untill, I press the switch off. This wave froms will produce nice sound (similar kind of as you posted.to be I never heard that sound..)where I have to connectspeaker with to 4 or 8ohms load.

If that is what you want, then I suggest you have another look at my circuit attached to post #12 of this thread. A 5%THD sine wave is going to be more than adequate for a 6 cycle tone burst!

Using a VCA and envelope generator to control two individual cycles of a 6 cycle burst is really overkill, IMHO.
Plus the fact that my SA571 modulation waveform would give you a triangle, not the modified square you are looking for.

I'm still not sure exactly what you are trying to achieve. It sort of sounds like you're trying to copy telephone tones. If that is the case, there are better ways of doing that than this way!!

I tried your ckt as you posted #12, attached simulation file. look at it.. final output wave form(yellow ) is giving square wave.. I adjusted values .. POT vlaues..(1M) for set trailngle GAIN, your ckt working brilliantly, upto opamp C , but opamp D in you ckt not giving sine wave.. ....