chip vs discrete

#1. I saw this cct that implemented a full-wave rectifier using an LM 324 (quad opamp) and two diodes for rectifying a signal. What advantage does this have over the conventional 4-diode bridge rectifier?

#2. How does an LM 3914 implemented as a zero-crossing circuit work? Does it offer any advantage over using the opamp-zener diode configuration?
Thanks for your replies.

aibelectronics said:

#1. I saw this cct that implemented a full-wave rectifier using an LM 324 (quad opamp) and two diodes for rectifying a signal. What advantage does this have over the conventional 4-diode bridge rectifier?

Click to expand...

A diode will drop 0.6V in the forward direction. A bridge rectifier uses four diodes and at any one time the signal need to go through two diodes so there is a 1.2V drop minimum. This is bad if your signal is only a few volts maximum or lower. Using a diode in the feedback path of an opamp would allow the opamp to increase its output to compensate this drop automatically so the rectification can work even with small signals.

Sorry I don't know the answer to your second question.