Capcitor selection value

Hi,

I have seen the following peak detector document on the internet and have following questions

1. Is it a half wave rectifier?

1. I expect to read different voltage values at different times and than sample them using ADC sampling at 500KHz. The diagram suggest that there is no path to discharge the capacitor 0.47uF once it gets charged. So, If I read +5 volts than how can I discharge the cap to read a differnet value later? I thought that may be I can add the switch across the capacitor to discharge it and control the timing of the ON and OFF by using the microcontroller. So, lets suppose after reading the value of 5 volts acorss the capacitor, I discharge it by turning ON the switch and then after micro read the value, it will turn OFF the switch and then wait for another value across the capacitor. But How will the micro know that the different value is available across the capacitor?

2. What is the role of the diode in the feedback loop?

1. How should I choose the value of the capacitor?

my input analog signal is 5 volts sine wave peak to peak with the fequency of 100KHz.

Thanks John