I need help in function generator

[andales]

Hey guys,

Can you please give me a schematic diagram of function generator using
oscillators

 

[ikalogic]

Hey guys,

Can you please give me a schematic diagram of function generator using
oscillators

saving the time of all my tutors here, the answer is google.com

 

[chemelec]

Hey guys,

Can you please give me a schematic diagram of function generator using
oscillators

Just do a search for an XR2206. It is one of Many Function Generators.

Need One? Just Email me.

 

[andales]

I am planning to build one without using ICs and it must be able to output sine , saw, square, triangular wave

 

[chemelec]

I am planning to build one without using ICs and it must be able to output sine , saw, square, triangular wave

LOTS OF LUCK!
To do all what the XR2206 does and with a Good Frequency Range, would require a Very Complex circuit.

 

[picbits]

I have built a couple using the MAX038 IC - not the cheapest in the world but pretty easy to get something knocked up.

 

[audioguru]

The MAX038 is not made anymore. It was a much better version of an old ICL8038 that is still being made. They are similar to an XR2206.

 

[Roff]

I am planning to build one without using ICs and it must be able to output sine , saw, square, triangular wave

Not even op amps? What are you, a masochist?

 

[Sceadwian]

andales, are you familiar with the term "Don't try to reinvent the wheel"? What you're talking about is the analog equivilant of creating a micro processor using only discrete logic IC's and flipflops.

 

[andales]

Well, if you are wondering why would i want to build a function generator using transistors and oscillators, heres is my answer:

"It has become a hobby of mine to build the insides of a ICs coz for me, it is the only way to understand how ICs work. Long time ago I built a decoder without using decoder ICs (74LS48 for example) , instead I used logic gates ICs to build a decoder inorder to better understand why 74LS48 can display 0-9. I have built a counter using flip flops without using some counter ICs, with the same reason as stated earlier"

How about crystal oscillators, can I use it to produce wave?

thanks for your help guys.

 

[andales]

What are you, a masochist?

I'm no freak'n saddist

 

[Roff]

I'm no freak'n saddist

A sadist is not the same as a masochist.

 

[evandude]

"It has become a hobby of mine to build the insides of a ICs coz for me, it is the only way to understand how ICs work. Long time ago I built a decoder without using decoder ICs (74LS48 for example) , instead I used logic gates ICs to build a decoder inorder to better understand why 74LS48 can display 0-9. I have built a counter using flip flops without using some counter ICs, with the same reason as stated earlier"

There's a huge difference between building a basic logic device out of individual logic gates, and developing a complex analog circuit that gives you specific waveforms and works across a broad frequency range. Digital is pretty easy, as long as your design isn't extremely flawed it should work pretty well at quite a range of speeds/frequencies. With analog (particularly in a function generator), you need linearity, and achieving that across a very broad range of frequencies is not so easy.

If you're truly crazy enough to attempt this, you ought to forget about doing it all at once and work on it in stages. For starters, you might want to try to build a decent op-amp, and a decent oscillator where you can reliably change the frequency over a huge range, so you can use them as building blocks if you ever get around to attempting the system as a whole.

But avoiding the use of op-amps, for example, is crazy. You say you used logic gate IC's in your previous logic designs, well why didn't you use discrete transistors instead? Probably because that would have resulted in a huge board, and not have even worked well anyway. The same could be said about op-amps. If you download the datasheet for the LM741, a very old and simple op-amp, you'll see about 20 transistors in it. If you really want to learn how they work, why not just try building one, playing with it, and then just use real op-amps in your other design to save the trouble. It's certain to work poorly, as you won't have the transistor matching you would in a single IC, not even counting all the other factors working against you, but you might be able to learn something from it. The problems of linearity and dynamic range and frequency response and all that are things that have already been dealt with by the people who designed op-amp IC's...

It's one thing to reinvent the wheel, it's quite another to reinvent an entire car. You said you built a logic decoder, well, if you later decided to build a more complex logic design that incorporated logic decoders, would you actually re-build your own elaborate logic design multiple times, or would you just go ahead and use commercial logic decoder IC's, now that you know how they work?
If you choose the former, well, I think you're nuts. If you choose the latter, then why not do the same with this function generator project? If you want to know how a certain part works, go ahead and build one, but refusing to use any IC's just to force yourself to do everything completely from scratch truly is masochistic, and pretty pointless, as you're sure to end up with a very poorly-working finished product despite spending FAR, FAR more time building it.

Now, since I get the feeling you are not going to give up on this easily, before you ask further questions about the details of a function generator, why don't you go download the datasheets for some commercial function generator IC's and look at how THEY get the job done. For instance, the datasheet for the old MAX038 has a block diagram of the whole system that is very useful. There are still other details, like how to generate sine/triangle/sawtooth waves, most of which you can also answer for yourself just by searching google and/or the forums.

At the very least, you should do your research so you know what you're getting into... Your basic questions about oscillators suggest that you don't yet realize what you're in for.

 

[Roff]

Check out these old Wavetek manuals. There is as much info here as you will need for discrete-component function generators.

 

[Hero999]

What about the usual questions people?

Frequency range? If it's fixed (say at 1kHz) then it'll be pretty simple, if it's variable (50mHz to 50MHz) then it'll be far more complecated.

Output impedance?

Output voltage?

Distortion?

 

[andales]

You say you used logic gate IC's in your previous logic designs, well why didn't you use discrete transistors instead?

done that already

You said you built a logic decoder, well, if you later decided to build a more complex logic design that incorporated logic decoders, would you actually re-build your own elaborate logic design multiple times, or would you just go ahead and use commercial logic decoder IC's, now that you know how they work?

I only built one, I dont have to build it multiple times coz I know how they work

Your basic questions about oscillators suggest that you don't yet realize what you're in for.

You're right, all i know is if I want to produce a frequency or signals I'm gonna need oscillators. That's all I know about oscillators. I still dont know how it really function

 

[dknguyen]

Oscillators are even more basic building blocks than logic gates. Perhaps you might want to try your hand at building some oscillators with transistors, crystals and inductors, capacitors before you undertake the signal generator you are talking about (it sounds like it's on the level of building your own oscilloscope). Have you tried building your own 555 timer yet?

 

[chinsoon]

Oscillators are even more basic building blocks than logic gates. Perhaps you might want to try your hand at building some oscillators with transistors, crystals and inductors, capacitors before you undertake the signal generator you are talking about (it sounds like it's on the level of building your own oscilloscope). Have you tried building your own 555 timer yet?

he just said that no IC can be used. he wants to build it from scratch.

by the way, if a 555 timer is used, a squarewave can be obtained right? subsequently with proper LC element, sine wave can also be generated from the squarewave isnt it?

 

[audioguru]

I would like to see him try to make an adjustable frequency LC filter.
For 20Hz the parts would be enormous.

 

[dknguyen]

he just said that no IC can be used. he wants to build it from scratch.

by the way, if a 555 timer is used, a squarewave can be obtained right? subsequently with proper LC element, sine wave can also be generated from the squarewave isnt it?

Yeah...and where did I mention using an IC? I just said he should learn to build oscillators first, for example building a 555 timer (from scratch).

You can generate a sinusoid from a square wave by filtering out all the harmonics above the fundamental.