Patent ID: 7626474

Claim:
An attenuation circuit comprising: a resistive divider coupled to an input node and an output node, wherein the resistive divider is configured to provide N:1 attenuation in a first range of frequencies of a signal received via the input node, the first range of frequencies extending from 0 up to a transition frequency; a capacitive network including first and second capacitive dividers arranged in a cascaded configuration, wherein: the first capacitive divider is coupled to the input node and being configured to perform a first attenuation in a second range of frequencies of the signal; and the second capacitive divider is coupled to receive the signal from the first capacitive divider and configured to perform a second attenuation in the second range of frequencies of the signal and provide the signal on the output node, wherein frequencies of the second range of frequencies are greater than the transition frequency, and wherein the total attenuation performed in the second range of frequencies is N:1; and a variable capacitance divider coupled in parallel with the second capacitive divider, the variable capacitance divider including first and second variable capacitors that, when adjusted, change an amount of attenuation provided in the second range of frequencies by the first and second capacitive dividers.