Im working on a student project to design a pcm system. I couldn’t find an adc that works with ac signals. How can i solve this problem ?

 

Do you want to measure the instantaneous voltage, peak AC voltage or just anything between +/-5V? What sample rate.
Must it be 8bit or can you use higher? What package do you require?

There are many bipolar ADCs around.
More info please.

 

I have a sampling rate of 10khz. And i need to convert instantaneous voltages. And it must be 8 bits

 

I also have flexibility to use external sample and hold circuits

 

Why only an 8 bit ADC? You can use 10 or 12 bits and throw the other bits out. It may be easier to find a 10 or more bit ADC.
Do you want SPI, I2C or what interface? Does it matter?
What is the processor you are wanting to use?
Lots of questions.
It does make it a lot easier to help if you explain your requirements better.

 

Use a simple opamp circuit-

1) Scale the signal down 50% to +- 2.5V (voltage divider)

2) Offset it positive by 2.5 V (differential amplifier and 2.5 V reference)

Result is then 0-5 V- you can feed this directly into a 5V ADC, which are very common.