Hi
i run a colpitts oscilator in multisim but the circuit not working

on the contrary the circuit in the Breadboard working what happen ?

 

Simulators are often not able to start an oscillator circuit. So you might get the oscillator running by inserting a single pulse. I think that BOB PEASE commented on that once.

 

Simulators are often not able to start an oscillator circuit. So you might get the oscillator running by inserting a single pulse. I think that BOB PEASE commented on that once.

thank ! if i change the value of coils L= from 10μF to 10mF and Rfcoil from 200μH to 300mH the circuit working !!

 

OK, I see that it is oscillating very well. It looks like the signal is 20 volts peak to peak, and not distorted.
Some sets of component values do not work. And some others work very well.

 

OK, I see that it is oscillating very well. It looks like the signal is 20 volts peak to peak, and not distorted.
Some sets of component values do not work. And some others work very well.

I have repeatedly watched Multisim users make a big mistake. You have made it, too. It is not taking into account the series resistance of the inductance. Are your windings made of superconductor?
Substitute reasonable values for series resistances.

 

I have repeatedly watched Multisim users make a big mistake. You have made it, too. It is not taking into account the series resistance of the inductance. Are your windings made of superconductor?
Substitute reasonable values for series resistances.

thank for the answer ! you mean the resistanece of real coil ? because the coil from the multi sim library is ideal

 

Here is the calculation with and without inductance resistances.

 

Here is the calculation with and without inductance resistances.

what is the name of simulation program ?

 

LTspice.
I wasn't hiding anything. If you look carefully, in the upper left corner of the picture you will see the name of the program.
In Multisim there are two models of the 2N2222A transistor. The first model is not the correct one. The second model is correct.
LTspice has a much wider list of factory models (with parasitic parameters) of inductors and capacitors compared to Multisim.
Also more convenient to search by volume, manufacturer, type and voltage or current.

 

LTspice.
I wasn't hiding anything. If you look carefully, in the upper left corner of the picture you will see the name of the program.
In Multisim there are two models of the 2N2222A transistor. The first model is not the correct one. The second model is correct.
LTspice has a much wider list of factory models (with parasitic parameters) of inductors and capacitors compared to Multisim.
Also more convenient to search by volume, manufacturer, type and voltage or current.View attachment 290568

With the previous values of L=10μΗ and L=200μF ( for RF coil choke) in LTspice the oscilator working ?

 

I am sorry.
See

 

I am sorry.
See
View attachment 290583
[/QU
In ltspice. Working this program is. Free?

 

One thing about oscillators is that not all of them start quickly, and not all of them produce a clean sine wave. And not all of them are equally stable. In addition, some combinations of L and C in the tuned circuit will be excessively sensitive to outside influences.
The circuit in post #7 seems to build amplitude rather slowly, as an example.

 

In ltspice. Working this program is. Free?

Simulator LTspice is absolutely free.
Download:
https://www.analog.com/en/design-center/design-tools-and-calculators/ltspice-simulator.html

Additional library download:
http://bordodynov.ltwiki.org/

 

Excuse me. I took a screenshot while the picture was being regenerated (updated). I will reload the picture on Monday.

 

Simulator LTspice is absolutely free.
Download:
https://www.analog.com/en/design-center/design-tools-and-calculators/ltspice-simulator.html

Additional library download:
http://bordodynov.ltwiki.org/

thank !

 

I am sorry.
See
View attachment 290583View attachment 290584

i practice what value for L i must choose L=10μΗ Lrf=200μF or L=10mH Lrf=300mH ?

 

It is more practical to use the following values: L=10μΗ Lrf=200μH. In general, this is a strange question. Do you need to have generation and don't care about frequency? Are you going to make a layout or do you only need calculation in Multisim?

 

It is more practical to use the following values: L=10μΗ Lrf=200μH. In general, this is a strange question. Do you need to have generation and don't care about frequency? Are you going to make a layout or do you only need calculation in Multisim?

the only difference is the frequnecy of oscillation in fisrt case the f0=357kHz and the second case f0=11.3 kHz and the impedance of rf coil is XRF=449 Ω and XRF=13 Ω . i aks according to theory what is the most consistent' value?

 

Excuse me. I took a screenshot while the picture was being regenerated (updated). I will reload the picture on Monday.

Hi again i put a noise source and the copliitts oscilator work in multisim