When it comes to powering noise-sensitive analog/RF applications, low dropout (LDO) linear regulators are generally preferred over their switching counterparts. Low noise LDOs power a wide range of analog/RF designs, including frequency synthesizers (PLLs/VCOs), RF mixers and modulators, high speed and high-resolution data converters (ADCs and DACs) and precision sensors. Nevertheless, these applications have reached capabilities and sensitivities that are testing the limits of conventional low noise LDOs. For instance, in many high end VCOs, power supply noise directly affects the VCO output phase noise (jitter). Moreover, to meet overall system efficiency requirements, the LDO usually post-regulates the output of a relatively noisy switching converter, so the high-frequency power supply rejection ratio (PSRR) performance of the LDO becomes paramount. With its ultralow output noise and ultrahigh PSRR performance, the LT3042 can directly power some of most noise-sensitive applications while post-regulating the output of a switching converter, without requiring bulky filtering.