| 摘要 |
A variable transconductance amplifier (100) including a variable attenuator stage (101A or 101B) coupled to a transconductance stage (103A or 103B). The variable attenuator (101A) includes first and second differential to single-ended transconductance stages (205, 207), each biased by a current device (201, 203). The variable attenuator (101A) receives a differential input voltage signal (VIN+, VIN-) and develops a current signal (ID). At least one reactive element (R1) is coupled between the pair of differential to single-ended transconductance stages. The transconductance stage (103A) includes first and second differential pairs (Q11-Q14) each having first and second control terminals and first and second output terminals. The first and second differential pairs are coupled to the first and second differential to single-ended transconductance stages, respectively, of the variable attenuator. The output terminals of the first and second differential pair are cross-coupled to develop a differential output current signal (IOUT+, IOUT-). The stages include electronically controllable current devices so that the overall transconductance may be when the input signal increases without distorting the output signal. |
