crystal oscillator question!!! THX

[Sommes]

How to adjust the oscillation frequency from the output frequency of 1MHz
crystal oscillator?
Thanks

 

[Phil Allison]

How to adjust the oscillation frequency from the output frequency of 1MHz
crystal oscillator?

** You will have to part with more details than that.

What is this oscillator ??

How much shift do you need?





............. Phil

 

[Sommes]

I am doing a analog project.
The topic: High stability variable oscillator
Select and test an appropriate digital oscillator circuit for producing an
accurate variable oscillation from 1kHz to 1MHz

What I think is I have to use crystal oscillator to make stable oscillation.
I will chose 1MHz crystal oscillation...after I may need to adjust 1MHz to
1KHz range.

Please let me know the right track...Thanks...

 

[Peter Parker]

I am doing a analog project.
The topic: High stability variable oscillator
Select and test an appropriate digital oscillator circuit for producing an
accurate variable oscillation from 1kHz to 1MHz

What I think is I have to use crystal oscillator to make stable oscillation.
I will chose 1MHz crystal oscillation...after I may need to adjust 1MHz to
1KHz range.

You won't be able to obtain a continuous coverage over that range.

However you could use divider chips to get frequencies that are submultiples
of 1 MHz.

One way to obtain that range is to use two oscillators (one crystal and one
variable) with the difference being 1-1000 kHz. However this won't be
particularly stable unless the variable oscillator is synthesised with a PLL
or similar.

Rgds, Peter

 

[Phil Allison]

"Sommes"

I am doing a analog project.
The topic: High stability variable oscillator
Select and test an appropriate digital oscillator circuit for producing an
accurate variable oscillation from 1kHz to 1MHz

What I think is I have to use crystal oscillator to make stable
oscillation.
I will chose 1MHz crystal oscillation...after I may need to adjust 1MHz to
1KHz range.

Please let me know the right track...Thanks...

** The question has undefined terms in it. How stable is "high
tability" - it should be given in ppm/ C. How variable is variable ? In
small steps or infinitely ?

A reasonably stable oscillator ( 500 ppm/C ) can be built with a few logic
gates plus Rs and Cs - I suspect this is what is being asked for.

A crystal derived one that varies in small ( ie 1 Hz steps ) would be a
MAJOR project.




................. Phil

 

[David L. Jones]

I am doing a analog project.
The topic: High stability variable oscillator
Select and test an appropriate digital oscillator circuit for producing an
accurate variable oscillation from 1kHz to 1MHz

What I think is I have to use crystal oscillator to make stable oscillation.
I will chose 1MHz crystal oscillation...after I may need to adjust 1MHz to
1KHz range.

Please let me know the right track...Thanks...

If you want a continous varying crystal derived frequency over that
range (which is very large) then your best bet is a Direct Digital
Synthesis (DDS) chip like the AD9835. Basically a single chip solution.
Although if it's an "analog" project, the DDS may not be suitable
because it uses digital techniques.
You may also want to consider a MAX038 waveform generator. Although it
is not crystal derived, it can be quite stable if using the right
components. The MAX038 uses "analog" techniques, so it may be more
suitable. Another single chip solution.
The MAX038 is easier to implement than the DDS chip.

Regards
Dave

 

[Mike Diack]

"Sommes"
Take a look at the Analog Devices AD95xx series of DDS chips.
These are a piece of cake to generate the range of frequencies you want.
You can also do it with a small fast microcontroller and a DAC (or an
R2R network). Jesper Hansen's minidds
http://www.myplace.nu/avr/minidds/
It's a ripper,and you can hack it into a sweepgen or anything else you
like. The truly masochistic would do it with Rs and Cs.
M

 

[Phil Allison]

"Mike Diack"

Take a look at the Analog Devices AD95xx series of DDS chips.

** Did you read the **question** at all Mike ?????????????

As an **analog project ** this is the OP's task :

" High stability variable oscillator.
Select and test an appropriate digital oscillator circuit for ..... "

The OP is likely at high school or TAFE and this is what some half witted
teacher has set for him to do.

The OP is so dim he has not supplied the necessary context for his
roblem - it has to be inferred.




............. Phil