Pierce Crystal Oscillator , Help with schematic

Thread Starter

ExpL0siV3Man79

Joined Jun 4, 2018
93
I am trying to make a pierce oscillator but I cant make it work... Any idea what's wrong with my schematic ? Many Thanks :)

pierce oscillator_ExpL0siV3Man79.png
link : http://tinyurl.com/y9bqcuwj
Transistor : 2N2222 NPN
P.S. Assume that the RLC circuit in the scematic is a 16MHz crystal resonator.


Mods Note:
Please upload the circuit to our forum, otherwise the thread may become useless someday when the links is gone.
The circuit already uploaded to the forum.
 

danadak

Joined Mar 10, 2018
3,577
You do not have proper DC bias on transistor.

The 1M probably way to high. Bias collector so that its ~ 1/2 V supply.

Also your approach with no emitter degeneration presents low Z
on LC tank, de-Q-ing the tank network bigtime.



Regards, Dana.
 

Thread Starter

ExpL0siV3Man79

Joined Jun 4, 2018
93
that's a coolpit's oscillator I think . I am trying to make a pierce oscillator :/ .
maybe this will help :

pierce oscillator2_ExpL0siV3Man79.png
http://tinyurl.com/y9rldodw
Reminder : Assume that the RLC circuit in the schematic is a 16MHz crystal resonator


Mods Note:
Please upload the circuit to our forum, otherwise the thread may become useless someday when the links is gone.
The circuit already uploaded to the forum.
 

Thread Starter

ExpL0siV3Man79

Joined Jun 4, 2018
93
The inductorless version:
That's what I found online and copied . The difference is that I didnt use a NOT gate IC but constructed one using an 2N2222A NPN transistor .Will this work ? Can anyone test this version with an oscilloscope and inform me if it's working ? I dont have such a device and I can't buy one right now . Is there a way I can test my oscillator my self without such a device ?? Many Thanks :)
 

Thread Starter

ExpL0siV3Man79

Joined Jun 4, 2018
93
can I change R1 to 1.5K Ohm and R2 to 1 M Ohm ?
P.S. Could you please add an output cable to the scematic so I know where the signal comes from ? Many Thanks :)
 
Last edited:

Bordodynov

Joined May 20, 2015
2,393
Install LTspice and my library and change the circuit and resistor and capacitor values. Also you can change the type of transistor. You have already written about the fact that 1 MegaOhm needs to be reduced! I subscribe to this. If you only have 1 mega Ohm resistors, put three in parallel!
 

Thread Starter

ExpL0siV3Man79

Joined Jun 4, 2018
93
Okay I put 3 1MOhm resistors in parallel and connected them as needed . I have a question...Well I don't understand the output ciquit...I added the extra capacitor but I can't figure out what is the T1 etc...:(
 

Bordodynov

Joined May 20, 2015
2,393
T1 is a long line (cable) with a delay of 5 nsec, which corresponds to (approximately) one meter of cable. The impedance is 50 ohms. Is not that what you wanted? The load is 50 ohms matched to the cable.
I advise you not to play cartoons, but install LTspice. At this forum this program is actively used and you will be helped by advice in case of difficulties.
 

Thread Starter

ExpL0siV3Man79

Joined Jun 4, 2018
93
I installed Ltspice , made a prototype , Now to test if it's working . How can I test the prototype ? Or I dont have to ?
 

Bordodynov

Joined May 20, 2015
2,393
The table shows the feedback resistors for the inverter on the CMOS transistors. The constant component of the voltage across these resistors is zero in this case. From this it follows that the value of the resistor does not affect the amplifier mode. When using a bipolar transistor, this is not the case. The mode of the transistor depends on the value of the resistor. Optimally, if the collector has about half the supply voltage, and for this the resistor in the base should be in BETA times more collector. And yet, this is the case when you should not be a dogmatist. If in my scheme you put 1 MegOhm, it will not work! And with my values works in a simulation. 1 MEGOhm only when BETA = 700.
 

Audioguru

Joined Dec 20, 2007
11,251
So I can't change R2 to 1MOhm ?
You must calculate the required resistor value from the hFE range of the transistor so that it has enough base current, but not too much. Using 1M you need a transistor with an hFE much higher than any transistor which is why it works with a Cmos inverter. A Cmos inverter draws an input bias current of ZERO.
 

Janis59

Joined Aug 21, 2017
767
RE:danadak, ""Bias collector so that its ~ 1/2 V supply""
Or say it slightly lighter, it may be between some 10% to 50% of Vcc if it is larger than U(be). The 50/50% is not the mantra at all, however the good thumbrule for beginning.
 
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