An input buffer circuit comprising: a first current source; a first differential control circuit, configured to generate a first bias voltage at the first couple terminal according to the input signals, and configured to generate first control signals according to the input signals; a second current source; a second differential control circuit, configured to generate a second bias voltage at the second couple terminal according to the input signals, and configured to generate second control signals according to the input signals; a third current source, configured to provide a first current according to the second bias voltage; a first differential output circuit, configured to receive the first control signals to generate output signals; a fourth current source, configured to drain a second current according to the first bias voltage; and a second differential output circuit, configured to receive the second control signals to generate the output signal.