Monolithic GaAs HBT p-i-n diode variable gain amplifiers, attenuators, and switches

The authors report on monolithic circuits integrating HBTs and p-i-n diode using a common HBT MBE structure. An HBT variable gain amplifier using p-i-n diode as a variable resistor achieved a gain of 14.6 dB, a bandwidth out to 9 GHz, a gain control range of >15 dB, and an IP3 of 28 dBm. A two-stage HBT p-i-n diode attenuator from 1-10 GHz and an X-band one-pole two-throw HBT p-i-n diode switch were also demonstrated. The two-stage p-i-n attenuator has over 50 dB dynamic range at 2 GHz and a maximum IP3 of 9 dBm. The minimum insertion loss is 1.7 dB per stage and has a flat response to 10 GHz. The X-band switch has an insertion loss of 0.82 dB and an off-isolation of 25 dB. The bandwidth is greater than 35% and the IP3 is greater than 34.5 dBm. These circuits consist of p-i-n diodes constructed from the base-collector MBE layers of a baseline HBT process. This is the first monolithic integration of p-i-n diode switch, variable gain control, and attenuation functions in an HBT technology without additional processing steps or MBE material growth