A SiGe HBT limiting amplifier for fast switching of mm-wave super-regenerative oscillators

For super-regenerative oscillators (SRO), a principal component that determines several aspects of the system response is the quench signal generation. The high oscillation frequency of mm-wave SROs enables fast quench rates that could well exceed 10 GHz. This is desirable because higher symbol rates and, consequently, higher communication data rates could be achieved. This work presents a limiting amplifier fabricated in a 0.13-μm SiGe BiCMOS technology (f_T = 300 GHz) for the generation of fast switching signals from an external RF sinusoidal source. The amplifier core is based on a modified differential Cherry-Hooper topology with embedded emitter followers, which is preceded by an active balun input stage. An additional tapered emitter follower output stage is implemented to drive 50-Ω loads. The amplifier delivers 27.3 dB of differential gain over a 25-GHz bandwidth with a total power consumption of 79 mW. The power consumption is only 42 mW when excluding the output 50-Ω driver that is only necessary for measurement. The circuit occupies an active area of only 100 μm × 150 μm due to its compact inductor-less design. It generates a high-speed differential output from a single input with a maximum peak-to-peak output voltage swing of 1.2 V and a rise/fall time of 5.6/6.0 ps at 20 GHz.