In this paper, a multi-mode RF power amplifier (PA) is proposed for the 4.8 GHz multi-standard applications. The RF power amplifier has two operation modes; class-AB operation for nonconstant-envelope modulated signals and class-F operation for constant-envelope modulated signals. The proposed class-AB (linear) mode power amplifier design can be used in IoT, LTE, 5G, and multi-standard RF transmitters, while the class-F (switching) mode power amplifier design is suitable for IoT-LPWAN and Bluetooth RF transmitters. The multi-mode operation is achieved by controlling the bias voltages of the driver and the power stages. The proposed multi-mode power amplifier is designed using a 130 nm CMOS process. The class-AB operation has a saturated output power of 23 dBm at 4.8 GHz, a power-added efficiency (PAE) of 29.5 %, an output third-order intercept point (OIP3) of 18 dBm, and an adjacent channel power ratio (ACPR) of -36 dBc for LTE 15MHz channel bandwidth. The maximum PAE of 28% under the class-F mode is achieved at an output power of 22.3 dBm. The PA occupies 0.88 〖 mm〗^2of the chip area, and the active area equals 0.5〖 mm〗^2. The proposed PA consumes 136 mW, and 26 mW in class-AB and class-F, respectively.