[SOLVED] [HELP] Design Pierce Oscillator 40Khz output

[darrylcapulla]

Design Pierce Oscillator to generate output frequency of 40khz.
Can anyone help me?? please

 

[BradtheRad]

The Pierce oscillator has a crystal stabilizing the frequency of oscillation.

Therefore you can use a 40 kHz crystal, or...

If you have, say an 80 kHz crystal, then you can make a Pierce oscillator for that frequency, and divide its output waveform by 2.

 

[E-design]

Here is a starting point for you. This circuit shows a low Q model for a 40 kHz quartz crystal. Depending on the actual crystal you will use the values of C1, C4, R3 and R6 may have to be adjusted to get the necessary phase shift to satisfy oscillation criteria.



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[Warpspeed]

If you already have a 40 Khz crystal, then the above circuit would be an excellent starting point.

A much easier way would be to use a much higher frequency crystal that is an exact multiple of 40 Khz, and digitally divide down the frequency.

Higher frequency crystals are much more active and easier to get oscillating. The lower series resonant crystals can sometimes be quite frustrating, and require much experimentation to get working.

 

[D.A.(Tony)Stewart]

Like this with CMOS inverter

what help you need?

THeory?
Math?
details?
Tradeoffs of stability, tolerance, phase noise, cost?
Using any active device?

It would help if you reply or close thread as solved.

 

[E-design]

I agree we need more info. There are many ways to make a 40 kHz oscillator. It was specified it to be of the pierce variety. We need to know the reason for this. Maybe it is a homework problem?

 

[darrylcapulla]

sorry for late reply,
i need is computation and design. i have sample design using bjt but in simulation i've done, it doesn't look like the sample.

do all Pierce Oscillator use crystal?

and yes, its a homework.




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computation for this?

 

[BradtheRad]

In simple terms the Pierce oscillator is made by adding a crystal to a Colpitts type. Just as there is more than one configuration of Colpitts, likewise there may be more than one configuration of Pierce type.

* You must drive the crystal so it oscillates at its nominal frequency, and it must cooperate with the transistor bias so that you drive the transistor at what's known as a 'good operating point'.

* You must choose component values so the circuit starts oscillating easily, and continues indefinitely.

* You must select L & C values which produce the desired resonant frequency, and the ratio of L:C needs to be compatible with Ampere levels within the circuit.