Patent ID: 7760028

Claim:
An unbalanced/balanced transformer circuit for receiving single ended input signal at an input terminal and providing a differential output signal across a pair of output terminals, the circuit comprising: a first branch including an input terminal for receiving a single ended input voltage signal, a first transistor, a first resistance connected between said input terminal and a first terminal of said first transistor to provide a current signal flowing through said first transistor, a second resistance connected to a second terminal of said first transistor for providing a voltage output signal, and an output terminal; a second branch including at least one second transistor, a third resistance for providing an output signal dependent upon a current signal flowing through said second transistor, and an output terminal; and current matching means for maintaining current flowing through said third resistance substantially equal to the current flowing through said second resistance, in dependence upon the output voltage signal across said output terminals, wherein the current matching means comprises voltage-sensing means for sensing voltage differences between the output terminals and providing a signal to the second transistor to adjust the current flowing therethrough.