An analogue calibration CMOS circuit for a time‐difference amplifier is presented and compared over a digital calibration scheme in terms of process and temperature variations. Time‐difference amplifiers (TA) are used in time‐to‐digital converters (TDC) for improving conversion resolution. In TA‐based TDC, global variations (process, temperature, and voltage) are dominant over local variations (mismatch) if analogue approaches are used over the digital ones, where the matching between many cells is highly required. Unlike the digital calibration circuit, the proposed analogue approach based on a charge pump improves the TA gain performance against process and temperature variations. The simulations of the proposed TA in a 180 nm CMOS technology showed a 12% reduction in process and temperature variations with a maximum power consumption of 130 μW at 100 MHz operation frequency.