i designed a clapp oscillator that must deliver 150 MHZ but in simulation in LTSPICE i fount 147 MHZ , can anyone help me plzzz

 

What do you think would change the frequency of the oscillator?

 

the capacitors C1 , C2 , C3 and the inductance L

 

the capacitors C1 , C2 , C3 and the inductance L

And...

 

the source resistance maybe

 

Are there no other components connected to the tuned circuit which could add capacitance?

 

the diode 1N4148 !!!

 

Yes, and...

 

i don't know , what should i do to have 150 MHZ ?? plz

 

How about the gate of the FET?
Every component has some stray capacitance including R1 in your circuit but that is going to be negligible here as there is 50pF in parallel with it.
Look up the capacitance of the diode and FET and redo the frequency calculations and see what you get.
To change the frequency you need to change one of the main frequency determining components.

 

yes the gate of the fet have a capacitance of 5 pF , how can I correct that without changing the others components values ??

 

The gate of the FET is in parallel with a 50pF capacitor, so you could reduce that 50pF to allow for the FET gate capacitance.
You could also change either L1 or C3.

 

L1 must be kept at 0.24uH because i'm following a model , what do you think about a value of 33pf for C1 and C2 ??

 

If you calculate the frequency using those values and including the diode and FET what do you get?

 

147MHz IS 150MHz due to the tolerance of the components. Some are +/- 20%.

 

147MHz IS 150MHz due to the tolerance of the components. Some are +/- 20%.

In real life, yes, but this is in a simulator.
And yes, I know about monte carlo.

 

Adjust the input values due to tolerance and get 150MHz.

 

by using these value the frequency calculated is 150 MHZ , in simulation i found 144 MHZ without diode and 141 Mhz with the diode

 

You have also increased C3 from your original circuit.
Off for my beauty sleep now.

 

hahaha if i keep the same value for C3 i find 154 MHZ