A self-biased voltage/current reference (VCR) generator is simple, but suffers from some Trojan states surviving the conventional start-up process. After demonstrating this problem by simulation, this paper reveals the mechanism by analysing all the feedback loops that cause multiple Trojan states. Based on the theory, an enhanced start-up circuit is proposed that can remove all Trojan states. Finally, the enhanced start-up circuit is embedded into a self-biased voltage reference generator, and designed in 28 nm CMOS process. The simulation results prove that the enhanced start-up circuit successfully eliminates all Trojan states in a wide temperature range for different process corners.