vco using LM139 or 339 don't want to work

dear all

i tried both cir. (they are from the datasheet) but now way no osc. at all , i tried to use many IC but now way

any tips thanks , i am using Orcad 14

thanks all
bye

As far as i understood you are just simulating the circuit and it seems not to be working. Be careful to use step voltage generator instead of batteries to generate V+. This because from the simulator point of view batteries are source active from infinite time, then all capacitors are open circuits and inductors are open circuits since the transient phase has finished at minus infinite time. In this case the lack of transient doesn't allow the oscillations to start.
If this doesn't work, please post also the spice diagram.

Hi Ahmed,
in my opinion your first diagram is wrong and never will work, the second one corresponds to the diagram given in the National Semiconductor LM139... datasheet, March 2004, page 13 - Typical Applications, Two-Decade High-Frequency VCO. Nevertheless, the simulation results don't correspond to the datasheet information (i.e. 700Hz <= fosc <= 100kHz for Vcontrol from +0.25V to +50V) - they are far from it. (Note that the LM139 supply voltage is +30V (V+) with the V- pin grounded.)
'albbg' wrote you cannot use batteries to generate V+ but it's not true, you can - but for the simulation to work properly (oscillations to begin) you have to set the initial voltages of the capacitors to zero (IC=0); if you don't do it, the simulator calculates the bias point first, setting the capacitor's voltages to the calculated value and then it starts the transient analysis from this "steady" state (therefore there are no changes in such a circuit and no oscillations can begin).

You now selected the wrong cicruit, as said by Eric Best. You confused +ve and -ve input of U82B.

Regarding oscillation startup, unlike a LC oscillator, a relaxation or astable oscillator will always start in simulation, without providing particular initial conditions. It should be also the case with the present circuit.

P.S.: Why don't you post your Orcad design files for reference?

thx soooooo much i didn't take care at all of such pins .......ummmmm altough both from a datasheets but two diff one

thx agaaaaaaaain
it works thx again