I want to know when you have divorced you wife, is there a time limit that you can take her back?
Based on the few of info you've provided in your Question we have three cases two of them for the talaq with an accepted turn back:
In case of a rij'i talaq (talaq were a turning back is possible)
You can take back your wife within the 'idah (waiting period). But you should have witnesses for that, this may mean you (I'd say preferably both) should speak it out in front of others, also read the verses from surat at-Talaq.
If you couldn't reconcile within the 'idah your talaq becomes valid and at this moment you are divorced and foreign people, so a new marriage contract is necessary if you want to get back together!
This is the case after the first and second talaq.
This is based on verse 2:229:
Divorce is twice. Then, either keep [her] in an acceptable manner or release [her] with good treatment. ...
And when you divorce women and they have fulfilled their term, do not prevent them from remarrying their [former] husbands if they agree among themselves on an acceptable basis. ...
which would apply in both cases.
You can also read in surat at-Talaq 65:1-2 which explain the importance of counting the days of the waiting period, because if you get back together before it ends you can stay together us husband and wife if not you are asked to let her go which means she isn't your wife anymore, but a foreigner unless you asked once again for her hand.
In case of the third talaq
You can only get together again if your wife married somebody else, and this marriage is consumed and got divorced, note that engaging somebody to be a mohalil (a man who marries your wife and divorces her, so that you may have her back) is haram. A marriage like this has a touch of mut'a -which is haram among sunni Muslims-. But the major reason for considering it haram are ahadith like in sunan ibn Dawod, sunan ibn Majah...
This is based on verse 2:230
And if he has divorced her [for the third time], then she is not lawful to him afterward until [after] she marries a husband other than him. And if the latter husband divorces her [or dies], there is no blame upon the woman and her former husband for returning to each other if they think that they can keep [within] the limits of Allah . ...
(Verse 2:232) would apply also once the wife is "free for marriage" again!
See also my answer on Are women who are divorced after the consummation entitled to maintenance? for more details.
there are 2 levels of divorce and taking back. first level is divorce initiation. after initiation you can easily take her back before iddah time has passed. when iddah is passed, and you invite witnesses to that event, second level of divorce happen and you become divorced, and you can remarry her at same level with other men, so, you can lose her after this. if she does not marry other man, you can remarry her later, if she agree, without time limit for remarriage. but there can be only 3 consecutive marriages with one man. at 3rd divorce you also has 1st level of divorce and iddah time. if you take your wife back within iddah time, second level of divorce does not happen, and that is not counted as one of 3 allowed consecutive divorces. (so, it is not full divorce, but divorce attempt). this is according to quran, see explanation in Just reciting "Talak" thrice commits divorce? .