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Crystal Oscillator

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ProFPGA

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i am trying to make a cystal oscillator with 2n2222 transistor , the usual collector feedback with crystal in series with base . But i am not getting anything out ? the crystal i am using is 32.5khz the bulky old ones . I tried the ckt with 9v dc and also with 5v dc .

I dont think i can go wrong with amount of resistor i am using for base biasing they 560ohm and in series emitter it the same value ?

i have also tried the ckt with 4mhz crystal , no output ???

any clues ??
 

Diver300

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Most Helpful Member
Post your circuit, please.

Watch crystals at 32.768 kHz are very different to drive than normal AT cut crystals. The watch crystals have a much higher ESR (Equivalent Series Resistance) so you need a very high impedance amplifier.
 

BrownOut

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That circuit won't work as drawn. I'm not an expert on osciallators, but you should find a diagram that has been built and is proven to work, and build it exactly as specified. Then, once you have it working, you can modify and experiment with it. Your circuit has no chance of working.
 

Diver300

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Most Helpful Member
As others have said, you need a collector resistor.

The bias resistors are far too low. The ESR of a 32.768 kHz is about 50 kΩ so you need an input impedance well above 1 MHz

The only oscillator circuit for a 32.768 kHz that I have seen uses a CMOS inverter. They need a resistor to bias them to the switching point and generally a 1 MΩ resistor is too low, so a 10 MΩ is used.

A quick google search finds:-

Fox Electronics Application Notes

http://www.elecfree.com/electronic/wp-content/uploads/2007/07/oscilate.gif
 

audioguru

Well-Known Member
Most Helpful Member
Look in Google for Transistor Crystal Oscillator Circuit and you will find lots of circuits.
 

ProFPGA

Banned
hi there , i am done with making myself a simple transistor oscillator .
does any one know about a oscillator IC , where u hook up a 4mhz crystal and a variable pot to its pins and it generates sine wave , square wave and saw tooth wave .

thnaks for the ideas and advice .
 

ProFPGA

Banned
nope , i have tried numerous transistor cystal oscillators.
none of them work, i have checked the crystals as well they are ok .
but they dont work with the ckts i make , my capacitor values could have varied , but would that make a huge diff ?? that nothing is coming out ?
 

ProFPGA

Banned
i have even tried the simplest the inerter gate , where u only have to connect the crystal to the two terminals of the inverter and load capacitor on both o/p and i/p to the gnd . nothing but noise ???
 
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