Get configurable product collection in magento

/* **
Get product Collection only configurable product
**
*/
                        $notAssocative=array();
$collectionConfigurable = Mage::getResourceModel('catalog/product_collection')
->addAttributeToFilter('type_id', array('eg'=>'configurable'));
foreach($collectionConfigurable->getData() as $notAss){
array_push($notAssocative,$notAss['entity_id']);
}
print_r($notAssocative);