The AD606 can operate above and below these limits, with reduced linearity, to provide as much as 90 dB of conversion range. A second low-pass filter automatically nulls the input offset of the first stage down to the submicrovolt level. Adding external capacitors to both filters allows operation at input frequencies as low as a few hertz. The AD606's limiter output provides a hard-limited signal output as a differential current of 1.2 mA from open-collector outputs. In a typical application, both of these outputs are loaded by 200 resistors to provide a voltage gain of more than 90 dB from the input. Transition times are 1.5 ns, and the phase is stable to within 3 at 10.7 MHz for signals from 75 dBm to +5 dBm.