A 24 GHz broadband SiGe HBT limiting amplifier

A broadband, high-gain, limiting amplifier implemented in 120 GHz silicon-germanium (SiGe) heterojunction bipolar transistor (HBT) technology and aimed at low-cost 10-20 Gb/sec applications is presented. The amplifier achieves a saturated differential midband gain of more than 42 dB and a 3-dB bandwidth in excess 24 GHz for a 10-mVpp (-40 dBm) input. A clear and wide-open eye diagram was measured under 10-Gb/s operation. The limiting amplifier has an input sensitivity of less than 12 mV/sub pp/ at a bit error rate (BER) of 10/sup -9/. All of the stages of the amplifier employ the modified differential Cherry-Hooper architecture to achieve a broadband gain response. The total power consumption of the chip is 550 mW off of a -5 V power supply. The total chip area is 0.945 /spl times/ 0.720 mm/sup 2/. This amplifier is compared with other published amplifiers based on a newly proposed figure-of-merit.