problem with prepare statement PDO

<?php

class sqlRepository extends PDO implements RepositoryInterface{
  protected $db;

  public function __construct($file){
    try{
      $this->db = new PDO("sqlite:" . __DIR__ . "/database.db");
      $this->db->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
    }catch (Exception $e){
      echo "Unable to connect";
      exit;
    }
  }

  public function all($tableName){
    try {
      $results = $this->db->query("SELECT * FROM $tableName");
      return $results->fetchAll(PDO::FETCH_OBJ);
    } catch (Exception $e) {
      echo "Unable to retrieved results";
      exit;
    }    
  }

  public function find($entity, $value, $field = 'id'){
    $statement = $this->db->preapre("SELECT * FROM :entity WHERE :field = :value");
    $statement->bindParam(':entity', $entity, PDO::PARAM_STR);
    $statement->bindParam(':field', $field, PDO::PARAM_STR);
    $statement->bindParam(':value', $value, PDO::PARAM_STR);
    $statement->execute();
    return $statement->fetchAll(PDO::FETCH_OBJ);
  }

}