mm-Wave Op-Amps Employing Simple-Miller Compensation, with OIP3/Pdc Ratios of 211 (10dB NF) and 144 (6.0dB NF) at 2 GHz

We here report two mm-wave amplifiers employing strong global negative feedback to provide very low intermodulation distortion, using a 500 nm InP DHBT technology. The amplifiers, similar to operational amplifiers, use simple-Miller compensation and have 25 to 35 GHz feedback loop bandwidths. The large loop transmission at 2 GHz provides a large reduction of closed-loop distortion at this frequency. The first amplifier, designed for lowest IM3 distortion at this technology node, showed 35 GHz bandwidth, 13.8 dB (S
₂₁
) gain, with 1005 mW dissipation - where 53.2 dBm OIP3 and 10 dB NF are observed at f
₁
, f
₂
= 1.950, 1.975 GHz. It is unconditionally stable from DC to 15 GHz. The second amplifier improves upon noise figure through less-strong feedback and minimal input padding resistance, showing 25.8 GHz bandwidth, 19.8 dB (S
₂₁
) gain, with 956 mW dissipation - where 51.4 dBm OIP3 and 6 dB NF are observed at f
₁
, f
₂
= 1.950, 1.975 GHz. It is unconditionally stable from DC to 8 GHz. These results represent a ~ 1.4 x bandwidth increase for an op-amp employing simple-Miller compensation, as well as ~ 2.0 and 1.4 x betterment in OIP3/P
_dc
ratio at f
_s
= 2-3 GHz, compared to state-of-the-art. We address considerations important to the application of negative feedback to mm-, microwave amplifiers, including the effects of interface impedances on stability, the effect of feedback upon return losses and noise figure, and the effect of frequency compensation and of feedback topology on closed-loop distortion.