Patent ID: 6094571
Filing Date: 2000-07-25
Classification: H03D

Abstract:
A differential mixer circuit for mixing a first differential input signal and a second differential input signal with a first differential mixing signal and a second differential mixing signal to thereby form a first differential output signal and a second differential output signal, the differential mixer circuit comprising:a first transconductance amplifier coupled to receive the first differential input signal;a second transconductance amplifier positioned in parallel with the first transconductance amplifier and coupled to receive the second differential input signal;the first and second transconductance amplifiers being matched with one another to form a matched pair of transconductance amplifiers;a first degeneration resistor coupled between the first transconductance amplifier and a common ground to thereby form a first current source resistor;a second degeneration resistor coupled between the second transconductance amplifier and the common around to thereby form a second current source resistor;the first transconductance amplifier, the second transconductance amplifier, the first degeneration resistor, and the second degeneration resistor forming a Class AB amplifier in which DC bias current changes with changes in the first and second differential input signals, the Class AB amplifier generating a first amplified signal and a second amplified signal;a multiplying stage coupled to receive the first and second amplified signals and the first and second differential mixing signals;the multiplying stage having a first multiplying portion coupled to the first transconductance amplifier to receive the first amplified signal, and coupled to receive both the first and the second differential mixing signal;the multiplying stage having a second multiplying portion coupled to the second transconductance amplifier to receive the second amplified signal, and coupled to receive both the first and the second differential mixing signal;the first differential output signal being formed by the first multiplying portion, and the second differential output signal being formed by the second multiplying portion; andthe first and second differential output signals being substantially linearly related to the first and second differential input signals.