transient simulation on ADS

[Kesarmahata]

hello,i am designing a differential oscillator on ADS. by transient simulation i am getting oscillation like this. How i can achieve continuous oscillation. i am attaching schematic and result here. is there anything wrong in modelling?

 

[stenzer]

Hi,
unfortunatly I cannot identify the used BJT. Nevertheless, I would check the datasheet of the used BJT and have a look on the stated β / h_fe values. Choose one of the stated minimum values and adjust your collector current source. The maximum base-resistor can be determined by

I_b = I_c/β
R_b,max = (Vcc1 - Vbe)/I_b

The required capacitor depends on your aimed frequency and can be determined by

t_on = C • R_b • ln[(Vcc1 + Vcc2 -Vbe )/(Vcc1 - Vbe)]

greets

 

[Kesarmahata]

thank you for your quick response. I am a student and completely new in ADS. I need to read lot of things . could you explain a little things to do it practically ? here is the schematic of tank circuit and cross coupled circuit.

 

[FvM]

How did you arrive at the feedback capacitor and base resistor values? It seems unlikely that they provide sufficient feedback to maintain oscillations. A systematic approach would measure the loop gain and adjust it to a value slightly above 1.

 

[pancho_hideboo]

Bias resistors for base, 120ohm are too small.
Base of BJT is biased by current not voltage.

1kohm under 1mA current source has no meaning at all.
Can you understand current source ?

Feedback capacitors 1pF are too small compared to resonance frequency of tank.

Totally you are too lack of very basic circuit knowledge.
Learn very basic things before EDA Tool Play.

 

[Kesarmahata]

hello sir @panchoo_hideboo. thank u for your reply. yes i understand current source and sorry for my mistake . and i really agree i need to read lot of things. everything we are doing on our own at home. your name is quite familiar to me on some blogs. you are really an active moderator. stay safe