I am trying to build an LCR meter.It involves measurement of phase and voltage.I am successful in finding out a way to measure the phase difference between the voltage across the DUT(Device Under Test) and the current through it.But am unable to find out a circuit for measurement of low-level AC voltage.
Can anybody please suggest me a circuit for that.

 

What frequency, what range of voltages?

 

Voltage is in mV range and frequency varies over 50Hz 100kHz

 

What do you mean by measure?
An op amp circuit can certainly be used to amplify the signal.

 

what if noise is there....

 

what if noise is there....

It most certainly will be. It always is.

 

You might want to look here" https://wiki.analog.com/resources/tools-software/linux-drivers/iio-impedance-analyzer/ad5933

A general circuit for measuring low level signals requires a reference that tells when the signal is there and when it isn't. It's called a lock-in amplifier. Take a look here http://www.thinksrs.com/products/lockin.htm for some very sophisticated lock-ins.

 

For low level AC to 100KHz, I use my audio analyzer and oscilloscope.

 

Also see: https://www.researchgate.net/public...als_buried_in_noise_for_embedded_applications

and http://www.analog.com/media/en/technical-documentation/data-sheets/AD630.pdf