This paper presents a low current, 100 MHz bandwidth envelope detector (ED). The targeted functions relate to the need for many on-chip envelope dependent control schemes for improvement of linearity, efficiency, protection circuits, etc. in CMOS-based transceiver and RFIC power amplifiers (PAs). Measurements from an integrated circuit including an envelope detector and an RF amplifier fabricated in CMOS 0.18 um show a detected envelope bandwidth of 110 MHz and a DC power consumption of 2.3 mW with a 1.8 V supply for operation at 1.9 GHz.