Abstract: Two variations of a continuous-time instantaneous companding filter are integrated in a 25 GHz bipolar process. Their −3 dB frequencies are tunable in the ranges of 1-30 MHz and 30-100 MHz. The dc gains are controllable up to 10 dB. The measured dynamic ranges for a 1% total harmonic distorsion are 62.5 dB and 50 dB, for the 30 MHz and 100 MHz filters respectively. At maximum cutoff frequencies, the filters dissipate 6.5 mW from a 1.2 V supply. The filters are simple, common-mode interference-resistant, class AB log-domain integrators, suitable for implementation in low-cost bipolar processes. They are suitable for realizing low-voltage filters with reasonable linearity and signal-to-noise ratio. ALL-NPN low distortion input and output interface stages can be added to the integrators. The filters can be used to realized high-frequency programmable filters.

Abstract: Two variations of a continuous-time instantaneous companding filter are disclosed. The filters are integrated in a 25 GHz bipolar process. Their −3 dB frequencies are tunable in the ranges of 1-30 MHz and 30-100 MHz. The dc gains are controllable up to 10 dB. The measured dynamic ranges for a 1% total harmonic distorsion are 62.5 dB and 50 dB, for the 30 MHz and 100 MHz filters respectively. At maximum cutoff frequencies, the filters dissipate 6.5 mW from a 1.2 V supply. Disclosed is a simple, common-mode interference-resistant, class AB log-domain integrator, suitable for implementation in low-cost bipolar processes. It is suitable for realizing low-voltage filters with reasonable linearity and signal-to-noise ratio. Compatible all-NPN low-distortion input and output interface stages are also disclosed. Also described is the potential of all the circuitry disclosed to realizing high-frequency programmable filters.