We propose a simple power-efficient sub-1-V fully integrated RF front end (RFE) for 2.4-GHz transceivers. It introduces the following innovations. First, a function-reuse single-MOS digitally controlled oscillator power amplifier (DCO-PA) with full supply utilization improves antenna-To-DCO isolation for better resilience to jammers. Second, a noninverting transmitter (TX) matching transformer with a zero-shifting capacitor suppresses the second-harmonic emission of the DCO-PA and allows a single-pin antenna interface for both TX and receiver (RX) modes eliminating the transmit/receive (T/R) switches in the signal path. Third, a push-pull low-noise amplifier (LNA) reuses the TX matching transformer for passive gain boosting that reduces power consumption. Fabricated in 65-nm CMOS, the RFE occupies merely 0.17 mm2. Through the functional merge of the oscillator and PA, it can transmit 0 dBm at RF, featuring 10.2% power efficiency when delivering the RF power as low as-10 dBm at a 0.3-V supply. Under a 0.5-V supply, the LNA shows 11-dB gain and 6.8-dB noise figure (NF) while consuming 174 mu W.