Linear V to I converter using MOS transistors

[write2rammy]

Hi all,
I am designing a VCO and so I am using a V to I converter and then feed this current to ring oscilator.. Here I require a linear relation between the input voltage and the output current. I tried using a simple transistor with V in Gate and current from Drain. But since i this trans is in saturation I get a non linear (square relation). Also due to huge current requirement (for wide range) I cant operate in linear region. Can anyone help me to design a linear V to I converter..

 

[poweric]

you can use a op

 

[write2rammy]

Can you please explain this ckt.. I know that its an enhancement of widlar ckt. So what effect does it have by amplifying the feedback from the one without amplifier.

 

[frankliner]

It is a voltage to current converter driving the mos diode of a current mirror.

The amplifier forces the input voltage across the resistor. I=V/R