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Design >> Analog Design >> Signal Generator Design
https://designers-guide.org/forum/YaBB.pl?num=1175470594

Message started by Happy Poppy on Apr 1^st, 2007, 4:36pm

Title: Signal Generator Design
Post by Happy Poppy on Apr 1^st, 2007, 4:36pm

Hello all,

I am trying to design a signal generator for SOC.
From my little knowledge of designing.. I should design the oscillator and several others block for the signal generator.
I am not sure what is the problem of designing oscillator ...i.e issues that I should consider..
I am stuck on how to start the design. i.e better if I use the spice or straight away with mixed signal schematics ( in cadence).
What is your best suggestions?
My plan in the designing the oscillator would be using switched capacitor to replaced the resistor..
I wanted the signal generator to produced sine, triangle and square wave at frequency from near DC to 50 Mhz.. :'(
Anyone please give me soem suggection?? or guide for it??
and I am considering low power od SOC..

Title: Re: Signal Generator Design
Post by didac on Apr 2^nd, 2007, 11:12pm

Hi,
I suppose the easiest way to start is using OP_AMP. Using one OP_AMP with positive feedback as a square generator(using a capacitor bank to control the frequency) the with an integrator you can generate the triangular wave and using a filter the sinusoidal. But I think that this topology will be very power consuming and with poor performance(you need a sharp filter to have a good sinusoid). Another option will be designing a sinusoidal oscillator(L fixed and variable C probably) then driving the sinusoidal to an OP_AMP that saturates(generating the square) and finally an integrator to generate the triangular wave, this topology has the drawback that you need to use an inductor an depends on the Q and the process varietions(Q will determine the power consumption).
This is my considerations, maybe looking a bit in IEEE will help you with your design.
Good Luck!

Title: Re: Signal Generator Design
Post by solidstate on Apr 3^rd, 2007, 3:15am

Hi,

Maybe you can generate the ramp and a rough sine wave digitally, and then use a DAC to output it. This would lower the filter requirements of the harmonics filter didac proposed. On the other hand, for 50 MHz signals, if you want any decent resolution, this is also going to cost you power..

Just an idea, I suppose..

Title: Re: Signal Generator Design
Post by Happy Poppy on Apr 3^rd, 2007, 3:39pm

Hi guys...

Thanx for the ideas...
I found something related to the signal generator ( generate triangle wave ) with ADC...
so I might try that one ..
I got some idea now to design signal generator..
I'll start with designing Op Amp..and connected it with the capacitance..
really helps.. thanx guys..let's see how it comes out... :o