Patent attributes
An amplifier circuit contains a first and second current branch, each branch comprising an input transistor and a cascode transistor. Inputs of the amplifier are coupled to control electrodes of the input transistors in respective ones of the current branches. The control electrodes of the cascode transistors are coupled to each other. A high frequency coupling is provided between the control electrodes of the cascode transistors and a node of the common current source, to copy substantially common mode voltage changes of terminals of the main current channels of the input transistors to voltage changes at the control electrodes of the cascode transistors. Thus, changes in the voltage difference between the voltages at the different terminals of each input transistor are substantially eliminated, preventing parasitic currents from the control electrode of the input transistor to the main current channel of the cascode transistors, that would reduce the common mode rejection ratio and thereby linearity of the amplifier.
