CMFB Fully differential and single ended OP_amps

[kenambo]

Hi..

Why dont we need CMFB circuits for single ended op-amps..

how to convert single ended opamp output into differential opamp output..

i want to implement it in CMOS process,,

expecting good architectures..
thanks

 

[eswar16518]

Hi
The main difference between single ended and dual output opamps is in its architecture particularly the type of load.

Ex: Single ended opamp has current mirror type of load, Here the gates of the two transistors in current mirror are shorted together and drain of left transistor is connected to its gate.......Hence the dc biasings of two outputs is adjusted equally based on the biasing current, so no need of an extra circuit like cmfb needed to manitain or adjust the similar common mode...

Where as the dual output opamp has gate biased transistors as loads and the gates are not shorted....Hence the dc biasing at the two output nodes are at different voltages, so we need cmfb type of circuits which can bring back the difference to zero and manitain the same common mode output, for dual ended opamps

As there is a connection betwee

- - - Updated - - -

Hi
The main difference between single ended and dual output opamps is in its architecture particularly the type of load.

Ex: Single ended opamp has current mirror type of load, Here the gates of the two transistors in current mirror are shorted together and drain of left transistor is connected to its gate.......Hence the dc biasings of two outputs is adjusted equally based on the biasing current, so no need of an extra circuit like cmfb needed to manitain or adjust the similar common mode...

Where as the dual output opamp has gate biased transistors as loads and the gates are not shorted....Hence the dc biasing at the two output nodes are at different voltages, so we need cmfb type of circuits which can bring back the difference to zero and manitain the same common mode output, for dual ended opamps

Thanks & Regards
Eswar