How to fix error after enabling CDbCache component in Yii1?

Question

Yii

The site works, everything is as it should be without problems.
I put it in the component

'cache'=>array( 
         'class'=>'system.caching.CDbCache'
),

refresh the page:

CDbConnection failed to open the DB connection: could not find driver

Usually such an error is due to an incorrect connection to the database. But with the connection everything is fine, this error disappears after I rob the code above from the config.