Patent ID: 8058909
Filing Date: 2011-11-15
Classification: H03F,H03L

Abstract:
1. A transconductance amplifier comprising: a first and a second voltage/current converting element for converting a first voltage signal to a current signal; a third and a fourth voltage/current converting element for converting a second voltage signal to a current signal; a common-mode current generating part for converting each first voltage signal and second voltage signal to a current signal, and further generating a common-mode current in accordance with a common-mode component of each current signal; a first current circuit for subtracting the common-mode component by using said common-mode current generating part from each current signal converted by each of said first to fourth voltage/current converting elements; a second current circuit for supplying a difference between (a) a current signal by using said first voltage/current converting element from which the common-mode component is subtracted by using said first current circuit and (b) a current signal by using said third voltage/current converting element as a first current output; and a third current circuit for supplying a difference between (a) a current signal by using said fourth voltage/current converting element from which the common-mode component is subtracted by using said first current circuit and (b) a current signal by using said second voltage/current converting element as a second current output, wherein said common-mode current generating part comprises a fifth voltage/current converting element and a sixth voltage/current converting element for converting the first voltage signal and the second voltage signal to current signals, respectively, wherein said common-mode current generating part further comprises a seventh voltage/current converting element supplied with a third voltage signal at a base or a gate, and generates a common-mode current including a bias current in accordance with the third voltage signal, wherein said transconductance amplifier has an output terminal and an inverting output terminal connected to an inverting input terminal and an input terminal, and a voltage generating circuit comprises a capacitance for grounding one output part of said transconductance amplifier in accordance with an oscillation frequency.