Pressure boosting device for a fuel injection system and fuel injection system

The pressure amplification device (10) has an inner piston (38) and an outer piston (25) arranged concentric to each other. The pistons are arranged in a housing. The inner piston is arranged in an axially displaceable manner in the outer piston. A control chamber (31) is formed by the outer piston and the housing. The control chamber is connected with a fuel return line in a switching position of a control valve (20). Another control chamber (44) is formed between the inner piston and the outer piston, which is connected with the fuel return line in the switching position.