voltage to freq.

[shamooooot]

I need to design a linear R to F converter ,I'm able to change Resis. to volt. linearly but I can't continue ,I tried to make it with the linear VCO but it didn't work in pspice schematic even if I plot it exactly as it's here :
http://www.seekic.com/forum/22_circuit_diagram/19893_LINEAR_VCO.html
the VCO in schematic :
https://www.electronicspoint.com/attachment.php?attachmentid=1215&stc=1&d=1289910538
Q1: to see the out. (sawtooth & square wave)of this ckt in the probe should I run dc/transient analysis cuz all I can see is a constant voltage in tran. on both amps. out. and in there's no DC sweep ?

Q2: how can I in the end show a probe of resistance vs frequency if pspice run dc (no time and freq.), transient(no dc sweep), ac analysis separetly ?

here's the ckt made :
https://www.electronicspoint.com/attachment.php?attachmentid=1216&stc=1&d=1289910538
as u can see all sources are dc and after the buffer everythin seems wrong ...
Q3: the capacitor in my ckt seems to has no effect at all ,why ?
THANX THANX THANX I appreciate any comment....

 

[shamooooot]

22 views no replyyyyyyyyyy ????!!!!!!!!!

 

[barathbushan]

hi i don't know much about the R to f conversion ,
is there a specific purpose to do this ??

also if you have trouble with pspice use other simulators like MULTISIM or
CIRCUIT WIZARD

 

[aharrison]

I suggest using a constant current source such as the Linear Technology type LT3092 to drive your variable resistance, and then connecting the resulting voltage to a voltage controlled oscillator such as Analog Devices type AD654.