High frequency compensation circuit for high frequency amplifiers

摘要

A cascode amplifier includes a cascode input stage that provides a first current in response to an input signal. A second current is also provided in response to the input signal, where the second current is a scaled and smaller version of the first current. The second current is low-pass filtered using parasitic capacitance present in a current mirror. A delayed mirrored current is applied to the emitters of the lower cascode transistor circuit to provide negative feedback. The current mirror amplifies the effect of the parasitic capacitance in the low-pass filter. An output node of the cascode amplifier has an associated parasitic capacitance. The parasitic capacitance at the output node in the cascode amplifier is compensated for by proper arrangement of the parasitic capacitance in the current mirror, such that the cascode amplifier is useful at higher frequencies. The improved cascode amplifier is suitable for monolithic integration.