Second order /spl Delta//spl Sigma/ modulators using AlGaAs/GaAs HBTS

We have successfully demonstrated one-bit, second-order delta-sigma modulators in a 50 GHz (F/sub t/) AlGaAs/GaAs heterojunction bipolar transistor process. The integrated modulator, consisting of a low-pass single bit modulator, clock generators and output buffers, has attained an SNR of 37 dB at a sample rate of 2 Gs/s for an oversampling ratio of 20. The circuit dissipates 1.92 W. To our knowledge, these are the first reported HBT delta sigma modulators.