A signature circuit in a semiconductor chip includes a signature program circuit configured to be programmed with signature information and to output a signature signal in response to the signature information; a signature output circuit configured to block the signature signal output by the signature program circuit during operation in a normal mode, and configured to pass the signature signal during operation in a test mode; and a pad-driving transistor directly coupled to the pad, configured to drive the pad during operation in the normal mode in response to an operation command, and configured to drive the pad during operation in the test mode in response to the signature signal output by the signature output circuit. The signature circuit outputs the signature information through a transistor for adjusting impedance to reduce a chip size by omitting an additional logic circuit for the signature circuit.