Schemes of two-half-period rectifiers on op amps with switching inputs in accordance with the polarity of the input voltage are given. The switching of inputs is performed by a control signal taken ...

You can combine a carefully chosen op amp, a low-threshold P-channel MOSFET, and two feedback resistors to make a rectifier circuit with less forward drop than a diode (Figure 1). The rectified output ...

And here it is, modelled using LTSpice. It is the same circuit as the classic simple precision rectifier (set to pass the negative half-sine), but with the non-inverting input of the op-amp connected ...