Welcome to EDAboard.com

Welcome to our site! EDAboard.com is an international Electronics Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.

Some VCO questions regarding amplitude

Status
Not open for further replies.

eric0825

Newbie level 6
Joined
Jul 3, 2006
Messages
12
Helped
0
Reputation
0
Reaction score
0
Trophy points
1,281
Location
Taiwan
Activity points
1,380
Some VCO issues

Deal all:
I am a rookie of IC design engineer~I got some problems recently...

1.While design VCO, how to estimate the VCO amplitude? I know it is equal to the bias current multiply by the equivalent tank resistance with a efficiency factor~but here the problem in real design is how to estimate the tank resistance? coz the model provided by foundry of the passive element is not just a resistance in parallel with ideal inductance but more complicated~so how to calculate it or simulate by EDA tool?

2. I've study many papers about VCO, but i can't still understand what differential amplitude and single-end amplitude is, does it means the amplitude reference to another VCO output and reference to ground?
 

khouly

Advanced Member level 5
Joined
Oct 20, 2003
Messages
2,368
Helped
461
Reputation
916
Reaction score
102
Trophy points
1,343
Location
EGYPT
Activity points
13,242
Some VCO issues

with eda tools , u can get the total equivalent resistance of the resonator "tank circuit" ,

or use the EDA directly to get the output power of the VCO "the amplitude"

the differential output is the voltage difference between the two output nodes , most of the VCO's now are fully diferential
about the single ended is the voltage of one of the outputs with reference to the ground

khouly
 

milkdragon

Member level 3
Joined
May 3, 2007
Messages
64
Helped
12
Reputation
24
Reaction score
7
Trophy points
1,288
Activity points
1,604
Re: Some VCO issues

To determine your tank impedance, the simpliest way is to put a ideal AC current source with magnitude of 1, do AC analysis then plot the voltage at that node, which is the impedance also
 

eric0825

Newbie level 6
Joined
Jul 3, 2006
Messages
12
Helped
0
Reputation
0
Reaction score
0
Trophy points
1,281
Location
Taiwan
Activity points
1,380
Re: Some VCO issues

Thanks for ur help~

Take inductor for example, I usually use the EDA tool to get the S-parameter of the inductor, thus i can get the Y-parameter or Z-parameter, then I calculate the equivalent parallel conductance from the real part of Y-para and equivalent series resistance from real part of Z-para, by the same way, i can also get the equivalent series or parallel inductance from imaginary part of Z-para or Y-para (because of the limited Q-factor, the equivalent series inductance is not equal to parallel ones), i am not sure if this method is correct? Because as i know, the imaginary part of Z-para and Y-para is also contributed by f the parasitic conductance of the inductor, it may result in error of the calculated inductance value.
 

jecyhale

Advanced Member level 1
Joined
Feb 19, 2008
Messages
403
Helped
54
Reputation
108
Reaction score
8
Trophy points
1,298
Location
China
Activity points
3,001
Re: Some VCO issues

eric0825 said:
Deal all:
I am a rookie of IC design engineer~I got some problems recently...

1.While design VCO, how to estimate the VCO amplitude? I know it is equal to the bias current multiply by the equivalent tank resistance with a efficiency factor~but here the problem in real design is how to estimate the tank resistance? coz the model provided by foundry of the passive element is not just a resistance in parallel with ideal inductance but more complicated~so how to calculate it or simulate by EDA tool?

2. I've study many papers about VCO, but i can't still understand what differential amplitude and single-end amplitude is, does it means the amplitude reference to another VCO output and reference to ground?

1. you can calculate. but some time the simulated result is better.
and the phase noise is impacted by the amplitude.

2, differential is the double of singal-end.
 

Status
Not open for further replies.

Part and Inventory Search

Welcome to EDABoard.com

Sponsor

Top