A 3-stage shunt-feedback op-amp having 19.2dB gain, 54.1dBm OIP3 (2GHz), and 252 OIP3/PDC ratio

We report here a 3-stage shunt-feedback configured operational amplifier using simple-Miller compensation demonstrating 19.2dB mid-band S₂₁ gain, P_DC = 1020mW. At 2GHz operation the amplifier shows 54.1dBm OIP3 and a record high OIP3/P_DC ratio = 252. Through the use of a 350GHz f_r, f_max 0.5um InP HBT technology, the loop transmission at low GHz operation provides a large reduction to the closed-loop distortion. The amplifier employs a differential topology, resistive pulldown biasing, large 6nH inductors to act as RF chokes, and a 6-finger (10μm L_e) output stage to increase P_out before the onset of waveform clipping. The loop bandwidth is greater than 30GHz, 5.5dB NF, and is unconditionally stable from DC-8.5GHz. The slope-3 breakpoint (S-3BP, where the IM3 spurs are 3dB greater than the expected slope-3 trend) is at P_out = 16.6mW/tone. The increases to OIP3/P_DC ratio represent >; 1.7× betterment in state-of-the-art. The circuit contains 24 HBTs and is 0.92×0.46-mm².