Voltage controlled current source

EDAboard.com Forum Index -> Analog Circuit Design -> Voltage controlled current source

Author

Message

nandu

Joined: 12 May 2005
Posts: 46
Helped: 1
Location: Timbuktu

21 Jun 2006 11:05 Voltage controlled current source

hi

I intend to design a ring VCO as shown in the figure. Could anyone suggest a voltage controlled current source that i could use to generate the control current (Ictrl)?

Google
AdSense
Google Adsense

21 Jun 2006 11:05 Ads

Sorry, but you need login in to view this attachment

nandu

Joined: 12 May 2005
Posts: 46
Helped: 1
Location: Timbuktu

22 Jun 2006 8:11 Voltage controlled current source

i tried doing this by changing the vgs of an input transistor and mirroring the current to the inverter stages. but the trouble is that i the current varies non-linearly and by a huge amount for a very small voltage range(of abt 0.2V) and then it moves into triode. so im getting an unreasonable large voltage-to-current gain over a very small input voltage range. i am looking for a VCCS with a moderate gain over a larger input volt range (say 1V). im using 0.18u tech with Vdd of 1.8V