Patent ID: 7071760

Claim:
A detecting circuit comprising: a double balanced mixer having a first output and a second output, the double balanced mixer providing a first output current at the first output and a second output current at the second output; a first filter circuit connected to the first output of the double balanced mixer, the first filter circuit including a capacitor and a transconductance circuit; and a second filter circuit connected to the second output of the double balanced mixer, the second filter circuit receives the second output current from the double balanced mixer, the double balanced mixer having a first transistor which applies a first current to a first node according to a first signal, a second transistor which applies a second current to the first transistor according to a second signal, a third transistor which applies a third current to the first transistor according to a third signal, and a first current mirror circuit which applies a first voltage to the first output according to a fourth current which is supplied to the second transistor, the transconductance circuit having a first power node connected to have a first electrical potential applied thereto, a second power node connected to have a second electric potential applied thereto, an input node, a first current source connected to the first power node, a second current source connected to the first power node, a third current source connected to the second power node, a first voltage supply circuit connected to the second power node, a fourth transistor having a control electrode connected to the input node, a first electrode connected to the first current source and a second electrode connected to the third current source, and a fifth transistor having a control electrode connected to the first voltage supply circuit, a first electrode connected to the second current source and a second electrode connected to the third current source.