VERY HIGH-FREQUENCY LOG-DOMAIN BANDPASS-FILTERS

A transistor-level all n-p-n differential log-domain integrator geared toward low-distortion very high-frequency (VHF) applications is propo sed. Systematic design steps are suggested and used to realize second and higher order balanced bandpass filters, based on the method of ope rational simulation of doubly-terminated LC ladders. We discuss the sp ecial sensitivity of log-domain integrators to small de biasing offset s, practical issues in the design of the input and output interface st ages, and the effect of parasitic resistors and capacitors on high-fre quency log-domain filters. Experimental results from a 0.8-mu m BiCMOS implementation of a single-ended 220-MHz biquad and a balanced 130-MH z fourth-order bandpass filter are reported, with emphasis on their di stortion characteristics.