The figure of the amplifier is shown in the following .the main amplifier is
a differential input and a differential output fold cascode.using two resistance to vary the gain.however, the input resistance should less than 1k due to the limitation of the input noise.In my design another resistance should larger than 1000k due to the loading effect.Any buffer should be use between output and the resistance to reduce loading effect.And the buffer should not reduce the output swing.
a differential input and a differential output fold cascode.using two resistance to vary the gain.however, the input resistance should less than 1k due to the limitation of the input noise.In my design another resistance should larger than 1000k due to the loading effect.Any buffer should be use between output and the resistance to reduce loading effect.And the buffer should not reduce the output swing.