In this paper, a new true random number generator (TRNG) based on a new variable differential ring oscillator has been presented. In this structure, the ring oscillator’s jitter is considered a random phenomenon. The jitter of the proposed ring oscillator is driven by thermal noise and flicker noise so that the generated jitter is random. In this paper, a new variable differential ring oscillator has been designed. The stage of this ring oscillator is changed randomly in order to create random jitter. A new differential delay cell has been proposed to boost the speed of TRNG and random jitter. The proposed random number generator (RNG) is robust against temperature variations of [Formula: see text]40–120[Formula: see text] and voltage variations from 0.8 to 1.8[Formula: see text]V. The proposed system’s bitrate is 50[Formula: see text]MB/s and its efficiency is 30.03[Formula: see text]Mb/mJ. This process has been implemented in the 0.18[Formula: see text]um CMOS process. Simulation results have been presented in Hspice software and cadence. The output bit images have been displayed by Matlab software.