please I'm struggling with the V to F conv. >>>>?

Discussion in 'The Projects Forum' started by shamooooot, Nov 16, 2010.

  1. shamooooot

    Thread Starter New Member

    Nov 16, 2010
    2
    0
    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 :
    http://forum.allaboutcircuits.com/attachment.php?attachmentid=24577&stc=1&d=1289907772
    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 :
    http://forum.allaboutcircuits.com/attachment.php?attachmentid=24578&stc=1&d=1289908540
    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....
     
  2. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    Your V6 exceeds the supply rails for U3's input. This will lead to unpredictable behavior in a simulation. With real parts, this can result in smoke. :eek:

    The LF411 is obsolete. You should select an opamp that is still in production.

    Be certain to keep the input voltages within the common-mode limits of the opamps being used. Frequently, this is Vee+1.5v to Vcc-1.5v; although the LM324 can sense input to the negative rail.

    The LM324 is a very old and slow opamp. You should select a more modern opamp.
     
  3. shamooooot

    Thread Starter New Member

    Nov 16, 2010
    2
    0
    thanks for reply ,but if you tell me what to use as integrator and as a schmitt trigger and their supply voltage I appreciate it.....
     
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