What are the power class definitions for 5G NR user equipment and how do they affect PA design?

What are the power class definitions for 5G NR user equipment and how do they affect PA design? 3GPP TS 38.101 defines multiple power classes for 5G NR UE (User Equipment), each specifying the maximum transmit power and the required PA performance: (1) FR1 power classes: Power Class 3 (default): maximum output power = 23 dBm (200 mW). This is the standard for smartphones. The PA must deliver 23 dBm at the antenna port (after all RFFE losses: typically 3-4 dB for filters, switches, and matching). PA output at the PA port: 26-27 dBm. Power Class 2: maximum output power = 26 dBm (400 mW). Used for fixed wireless access (FWA) devices and some high-power smartphones. Requires a more powerful PA (29-30 dBm at the PA port). Increases the uplink coverage by approximately 3 dB. Power Class 1: maximum output power = 31 dBm (1.26 W). Used for vehicle-mounted UE and FWA CPE. Requires a high-power PA (GaN or GaAs, 34-35 dBm at the PA port). (2) FR2 power classes: Power Class 1: maximum EIRP = 43 dBm. Used for CPE (Customer Premises Equipment) with large antenna arrays. Power Class 2: maximum EIRP = 33 dBm. High-end smartphones with 4-module AiP configuration. Power Class 3: maximum EIRP = 23 dBm. Standard smartphones (default for FR2). Power Class 4: maximum EIRP = 34 dBm. Enhanced mobile broadband devices. (3) PA design implications: for FR1 Power Class 3 (23 dBm): PA technology: GaAs HBT (mainstream) or CMOS (emerging for cost reduction). PAE requirement: > 35% at 23 dBm (to manage heat and battery life). Linearity: meet EVM ≤ 3.5% for 256QAM at rated power. This requires DPD or ET (envelope tracking). The PA typically achieves 30-33 dBm P1dB, operating at 7-10 dB back-off for 256QAM. For FR1 Power Class 2 (26 dBm): PA must deliver 3 dB more power. This doubles the DC current and heat dissipation. The PA die area increases by approximately 50%. Higher power also tightens the adjacent channel leakage (ACLR) budget.