Do you have a particular integrated circuit in mind?

Dear vasudev,

I have implemented a single ended to differential amplifier in the following way :

 The circuit is composed of two amplifiers. One amplifier acts as a buffer and creates a voltage, Vout+. The second amplifier inverts the input and adds a reference voltage to generate Vout-. Both Vout+ and Vout- range from 0V to 2.5V. The difference, Vdiff, is the difference between Vout+ and Vout-. 

Here, you can choose output common mode voltage Vcm (common mode voltage by resistors and Vref ). In simple case, Vcm= 0.5* Vref. so basically with proper resistors we can set up common mode.

Hope, my answer helps You.

:) :)

Dear Val Martin,

Yes I have a circuit in my mind. It is normal differential amplifier in which input is connected to only one input ,other is connected to biasing voltage.

Dear Vasudev,

this is what i have written in my reply, one input is kept at input and second given a Vref.

regards

Dear Anuraag

Thanks for your reply. You have mentioned with some resistors(how?) we can set common mode...This is the doubt what I have? exactly how we will set common mode voltage .It is not like fully differential output, in which we can set it by using CMD and comparator.

The resistors come in the equation and in the circuit, same voltage ( Vin= Vref) will appear for a value R3=R4, but if u put other values common mode will not happen.

I hope this page give you an idea about gain setting resistors for Diff Amp.

http://www.electronics-tutorials.ws/opamp/opamp_5.html

Dear  Khan and Misra

First of all thanks .

I am not asking about Op-Amp case. Exactly I am asking about for the following circuit.

Please give me detailed explanation. I am not getting how to set the common mode for this circuit.

To get a common mode voltage of about 5v and a differential voltage of 100mV, proceed as follows: V1 is applied to one input and V2 to another input. Output is (V2-V1)*DMG + common mode effects. CM is actually 5.05V, while DM is [100*50/51]mV. The DM and Cm signals are at same frequency!

Set one input as 5V and another as 5.1V. One method of doing this is to have a 5.1V from function generator and get 5V from this through a divider of say 1k and 50k.

 In general Cm is 50 hz while DM may be 1kHz. One can get this  as follows. Connect V1 through 1k to 5V, 50 Hz and through 50k to 5V 1khz. Connect V2 to same 5V 50 hz through 1k, but return it to ground through 50k.. one can simulate all these if necessary using circuit maker or p Spice. You can make small changes as necessary to get exactly Cm and DM voltages. .

 You can get any other combination of Cm and DM voltages using this method of resistive summing. If you change 1k above to 100 ohms, DM signal will be about 10mV. you can raise or lower the CM voltage by setting the output of 50 hz generator.

 Does this help?