When an input voltage is positive, the output of ICA is negative and diode D does not conduct; hence the outp
ut of ICB is positive. On the other hand, when the input is negative, the output of ICA is positive. D will conduct and cause the absolute value, expressed as a positive voltage, to appear on the noninverting input of ICB and on the circuit"s output. The circuit"s dynamic range extends from zero to the point at which the op amp saturates. The bandwidth is determined by the characteristics of the diode and the high-frequency performance of the op amp.