Magento2 increase dynamic field size

This way I have added dynamic field in store config. The issue is this text field values are going unreadable. How can I increase size of this fields to look it more clearer.

protected function _prepareToRender()
{
    $this->addColumn(
        'username',
        [
            'label' => __('Username'),
            'class' => 'required-entry',
        ]
    );
    $this->addColumn(
        'password',
        [
            'label' => __('Password'),
            'class' => 'required-entry',
        ]
    );
    $this->addColumn(
        'companyid',
        [
            'label' => __('Company Id'),
            'class' => 'required-entry',
        ]
    );

This way I have addded code. Please advice.