Patent ID: 7760003

Claim:
A controllable resistive circuit for providing a variable resistance, said controllable resistive circuit comprising: a first transistor having a first end, a second end and a third end, the first end of first transistor being a gate thereof; a capacitor having a first terminal coupled to the first end of the first transistor and a second terminal coupled to a reference node; a charging unit for charging the capacitor in a first period, the charging unit comprising a second transistor having a fourth end, a fifth end connected to a steady voltage supply and a sixth end connected to the first end of the first transistor; and a discharging unit for discharging the capacitor in a second period, the discharging unit comprising a third transistor and a resistor, the third transistor having a seventh end connected to the fourth end of the second transistor, an eighth end connected to a third terminal of the resistor and a ninth end connected to the second terminal of the capacitor, and the resistor further has a fourth terminal connected to the first end of the first transistor, wherein the variable resistance of the controllable resistive circuit is determined based on the equivalent resistance between the second end and the third end of the first transistor, the first period and the second period do not overlap, and the coupling between the first terminal of the capacitor and the first end of the first transistor is not through an operational amplifier.