| 摘要 |
PURPOSE: A transconductance variable circuit of a transconductor circuit and a variable bandwidth filter circuit by using the same are provided to vary the transconductance linearly. CONSTITUTION: A transconductance variable circuit of a transconductor circuit includes a first and a second amplifiers(MN21,MN22), a resistor(R21), a first and a second bias current sources(IB21,IB22), at least one resistor and at least one switches(SW21,SW22,SW23,SW24). Each of the first and the second amplifiers(MN21,MN22) controls the amount of the current flowing from the first terminal to the second terminal in proportion to the voltage applied to the third terminal. The resistor(R21) is connected between the second terminals of the first and the second amplifiers(MN21,MN22). Each of the first and the second bias current sources(IB21,IB22) is connected between the second terminals of the first and the second amplifiers(MN21,MN22) and the ground, respectively. And, the resistor and the switches(SW21,SW22,SW23,SW24) are connected between the second terminals of the first and the second amplifiers(MN21,MN22) in serial. |
