Design and modeling of an ultra-wideband low-noise distributed amplifier in InP DHBT technology

Abstract

This paper reports on an ultra-wideband low-noise distributed amplifier (LNDA) in a transferred-substrate InP double heterojunction bipolar transistor (DHBT) technology which exhibits a uniform low-noise characteristic over a large frequency range. To obtain very high bandwidth, a distributed architecture has been chosen with cascode unit gain cells. Each unit cell consists of two cascode-connected transistors with 500 nm emitter length and ft/fmax of ~360/492 GHz, respectively. Due to optimum line-impedance matching, low common-base transistor capacitance, and low collector-current operation, the circuit exhibits a low-noise figure (NF) over a broad frequency range. A 3-dB bandwidth from 40 to 185 GHz is measured, with an NF of 8 dB within the frequency range between 75 and 105 GHz. Moreover, this circuit demonstrates the widest 3-dB bandwidth operation among all reported single-stage amplifiers with a cascode configuration. Additionally, this work has proposed that the noise sources of the InP DHBTs are largely uncorrelated. As a result, a reliable prediction can be done for the NF of ultra-wideband circuits beyond the frequency range of the measurement equipment.

InP DHBT Single-Stage and Multiplicative Distributed Amplifiers for Ultra- Wideband Amplification

“…The cascode configuration is favoured for the high input-output isolation it offers, as well as the high output impedance which advantageously reduces the loading on the output transmission line of the DA [29], [46]. To improve bandwidth performance, the input transmission line is scaled down by a factor ζ ≈ 0.5 and peaked by a shunt capacitance C peak = 1 2 C π , where C π is the input (baseemitter junction) capacitance of the active device [24], creating a similar effect to the application of a radial stub [47]. The loss compensation technique described in [24] was employed, involving the addition of peaking inductances L cc and L ce to the cascode gain cell, with L cb added to maintain stability [24], [25].…”