Removal of Balun between LNA and mixer lead to the use of single-ended passive mixers in place of its differential counterparts. But the single-ended topology resulted in the variation of IIP2 performance of mixers across temperature and process corners as well as across different frequencies of operation. In this paper, we propose a threshold voltage tracking circuit in 14-nm technology to bias the passive direct-conversion single-ended mixers such that it enhances the IIP2 performance of mixers up to 20dB across temperature and process corners. This design includes a temperature-dependent bias voltage generation circuit with different slopes over temperature which can be varied with a step size of nearly 8mV and an additional DC voltage calibration circuit to generate differential bias voltages independently in I and Q channels. Two independent sets of 4-bit digital controls are used to vary the device size as well as the bias current used to bias the device in the circuit. This enables us to generate the mixer bias voltages with different slopes over temperature to employ across different frequencies of operation, temperatures and process corners.