Attenuator circuit operating with single point control

摘要

An attenuator circuit uses single point control to adjust the attenuation levels between first and second nodes. The attenuator is set-up as a pi -network with a pass transistor and first and second shunt transistors. Capacitors are coupled in the drain and source conduction paths of the first and second shunt transistors for DC isolation to float the shunt transistors. A control voltage applied at the drain of the pass transistor and the gates of the first and second shunt transistors controls the attenuation level. A parallel resistor and capacitor combination at the drain of the first shunt transistor provides tuning to match the input impedance of the attenuator to the sourcing circuit.