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VCO transient analysis

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umberabbas

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Hello,

I am designing a basic LC oscillator and want to see its transient response. However, when i run the simulation, it doesn't oscillates at all. Does anybody have any guide to resolve such issue?
 

Set initial current for inductor.

Then set UIC as transient analysis option, if you use SPICE.
 

Use trap integration method instead of gear or gear2, and use initial voltage for the capacitor or current for the inductor.
 

Please give more detail like schematic, so we have something to look at.
 

Screenshot.png

I am designing this LC VCO in cadence. Please have a look and suggest me what should i do?
 

When i run the simulation, it is giving this type of error.

The following branches form a loop of rigid branches (shorts) when added to the circuit.
V0: p (from vdd to 0)
 

Screenshot1.png

I deleted V0 and this is the output. I want the VCO to resonate at 60 GHz which means it should oscillate somewhere near 0.0166ns. What further steps should be taken in order to get the oscillator runs at the desired time period?
Furthermore, Please highlight how to write an expression for frequency in the calculator?
 

Can you understand Can you understand osciilation condition ?

Is a negative impedance enough large ?

Show us netlist.
 
Last edited:

Screenshot3.png

Yes i know about the Barkhausen criteria and the start up condition. Maybe I am making a mistake when i am implementing it in the circuit.
 

Screenshot-1.png

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Screenshot-1.png

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Applies a current kick to a specified node.
Sometimes you need to experiment with the pulse amplitude.

Code:
//V0 (vdd! 0) vsource dc=1.2 type=dc
V1 (vdd 0) vsource type=dc dc=1.2

Ikick0 (vdd net014) isource type=pulse val0=0 val1=Ibias \
delay=1n width=(1/60G)/2 rise=(1/60G)/2 fall=(1/60G)/2 \
period=10

Ikick1 (vdd net7) isource type=pulse val0=0 val1=-Ibias \
delay=1n width=(1/60G)/2 rise=(1/60G)/2 fall=(1/60G)/2 \
period=10
 
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