crystal controlled astable oscillator problem

[neazoi]

hello I have built this astable oscillator in 12MHz version using fast transistors (ft=1100MHz) **broken link removed**
Is there any way way to make the output more square like instead of triangular?

 

[efron]

hello I have built this astable oscillator in 12MHz version using fast transistors (ft=1100MHz) **broken link removed**
Is there any way way to make the output more square like instead of triangular?

Hi Neazoi,

Just to understand your need. You are requiring a 12MHz square signal.

Am I understanding correctly ?

Efron

 

[neazoi]

Yes, all I need is a 12MHz square wave oscillator using just transistors and crystal, not opamps

 

[Tahmid]

Hi,
Take a look at these if you can make do with gates:
Thomas Scherrer Crystal Oscillator Circuits
**broken link removed**
www.northcountryradio.com/PDFs/column007.pdf

There are a few transistorized circuits in the last link.

Hope this helps.
Tahmid.

 

[efron]

Yes, all I need is a 12MHz square wave oscillator using just transistors and crystal, not opamps

If you could limit the frequency to 10 MHz, Tahmid's proposal in his first or second link is a good and practical approach.

For higher frequencies, I can only suggest to use transistor-based XTAL oscillator with a very high gain at the amplifier stage, so that the output will be seen as a square signal because of the saturation of the transistor.

Would you know how to do that ?

 

[neazoi]

If you could limit the frequency to 10 MHz, Tahmid's proposal in his first or second link is a good and practical approach.

For higher frequencies, I can only suggest to use transistor-based XTAL oscillator with a very high gain at the amplifier stage, so that the output will be seen as a square signal because of the saturation of the transistor.

Would you know how to do that ?

Thank you all for the schematics. Limiting the frequency to 10MHz sould be not much of a problem.
You see I have already tried to build one using inverters made out of transistors but it did not work...
But the original circuit from the author worked using 74HCxx and not 74LSxx and my gates were built using DTL and TTL

I have thought about the limiting amplifier solution you propose and this is of much interest but I cannot find any schematic on the web Maybe you could help a bit?

 

[efron]

I have thought about the limiting amplifier solution you propose and this is of much interest but I cannot find any schematic on the web Maybe you could help a bit?

I will come with a proposal in a couple of days as right now I have no spare time :-(