PDO Driver Missing? EE 2.11.7

Hello,

I want to use PDO instead of mysqli.

config/database.php: $db[‘default’][‘dbdriver’] = ‘pdo’;

Log Error: require_once(*****/system/codeigniter/system/database/drivers/pdo/pdo_driver.php): failed to open stream: No such file

I downloaded the latest ExpressionEngine 2 Version (2.11.7) from this Site.

Can anybody help me? I think it should be possible to use PDO (https://expressionengine.com/forums/archive/topic/218455/why-no-pdo-database-driver-documentation)?