| Author |
Message |
asicpark
Joined: 14 May 2004
Posts: 41
|
 23 Aug 2006 18:56 how to reduce the gain of the VCO |
|
|
|
|
Hi all,
I want to reduce the gain of the VCO to make phase noise improve.
Power is 1.8V, center freq is about 500MHz and this is not a freq synthesizer
so that there is no need for wide range of freqency tuning range.
I use the differential amp with symmertric load as a delay cell and design the center frequency comes out at vdd=1V. In that case the resistor is so small
that the vco gain exceed over 1GHz/V. I just want to make it under 1~3 hundred
MHz. But I don't know how to make it.
Does anyone who know about this?
Thanks in advance.
|
|
| Back to top |
|
 |
jfyan
Joined: 03 May 2006
Posts: 199
Helped: 22
Location: shanghai,china
|
| 24 Aug 2006 1:53 Re: how to reduce the gain of the VCO |
|
|
|
|
| asicpark wrote: |
Hi all,
I want to reduce the gain of the VCO to make phase noise improve.
Power is 1.8V, center freq is about 500MHz and this is not a freq synthesizer
so that there is no need for wide range of freqency tuning range.
I use the differential amp with symmertric load as a delay cell and design the center frequency comes out at vdd=1V. In that case the resistor is so small
that the vco gain exceed over 1GHz/V. I just want to make it under 1~3 hundred
MHz. But I don't know how to make it.
Does anyone who know about this?
Thanks in advance. |
hi,
try in this way:
as we know, Kvco~1/(NCload),and ~[1/(Ibias)]^1/2,so i think, increase the delay cell number and load capacitance, or increase the baising current if power is permitted.
good luck.
jeff.yan
|
|
| Back to top |
|
|
chenmy
Joined: 18 Aug 2006
Posts: 17
Helped: 2
|
| 24 Aug 2006 17:22 how to reduce the gain of the VCO |
|
|
|
|
Hi, so ur VCO must have a voltage to current converter, maybe a diff pair,right?
Increasing the W/L of the diff pair to reduce the voltage to current gian will help!
Good luck!
|
|
| Back to top |
|
|
