1. A transconductor circuit comprising a transconductor (30, 35) coupled to a supply rail voltage source (Vdda) and at least one MOS resistor (R) comprising a MOS transistor (84, 86) whose source-drain path is coupled to the transconductor, resistance tuning means (96) coupled to the supply voltage rail and having an output for supplying a control voltage (cntrl) to a gate electrode of the MOS transistor, whereby the resistance value of the MOS resistor tracks changes in the transconductance of the transconductor due to tuning effected by altering the supply rail voltage (Vdda).
2. A transconductor circuit including a balanced transconductor comprising a first and a second single ended transconductors (30, 35), each having an input (40, 45) and an output (20, 25), MOS resistors respectively comprising MOS transistors (84, 86) having their source-drain paths coupled between respective first and second input terminals (10, 15) and the inputs (40, 45) of the first and second single ended transconductor (30, 35), a differential transconductance (200) coupled between the first and second input terminals (10, 15) and the inputs (40, 45) of the single ended transconductor (30, 35), a source of a common supply rail voltage (Vdda), and resistance tuning means (96) coupled to the common supply rail voltage source for supplying a control voltage (cntrl) to gate electrodes of the MOS transistors for tuning the resistance of the MOS resistors (84, 86).
3. A circuit as claimed in claim 1, characterised in that the resistance tuning means comprises means coupled to the supply rail voltage source for deriving a voltage (Vcm\u2212\u0394V) offset from a common mode voltage (Vcm) of the transconductor(s) and means for deriving a control voltage (cntrl) from said offset voltage, which control voltage is applied to gate electrode of each of the MOS transistors.
4. A circuit as claimed in claim 3, characterised in that the means for deriving a control voltage (cntrl) comprises a control loop including a parallel connection of a single ended transconductor (108) and the source-drain path a MOS transistor (110) emulating a MOS resistor, an input node (106) of the control loop being coupled to means (102) for supplying the voltage (Vcm\u2212\u0394V) offset from a common mode voltage, and an integrating stage having an input coupled to an output node (112) of the parallel connection and an output coupled to the gate electrode of the MOS transistor.
5. A circuit as claimed in claim 4, characterised in that the means for deriving the offset voltage comprises a transconductor (102) having a quiescent voltage lower than that of the single ended transconductor means.
6. A circuit as claimed in claim 4, characterised in that the means for deriving the offset voltage comprises a transconductor (102) comprising PMOS and NMOS transistors having dissimilar properties which produce a quiescent input voltage of the order of half the supply rail voltage.
7. A circuit as claimed in claim 1, characterised in that the or each MOS resistor comprises a NMOS transistor.
8. A filter circuit including a balanced transconductor comprising a first and a second single ended transconductor means (30, 35), each having an input (40, 45) and an output (20, 25), first and second MOS resistors respectively comprising first and second MOS transistors (84,86) having their source-drain paths coupled between respective first and second input terminals (10, 15) and the inputs (40, 45) of the first and second single ended transconductor means (30, 35), a differential transconductance (200) coupled between the first and second input terminals (10, 15) and the inputs (40, 45) of the single ended transconductor means (30, 35), and a source of a common supply rail voltage (Vdda), frequency tuning means for tuning the filter by adjusting the common supply rail voltage and resistance tuning means (96) coupled to the common supply rail voltage source for supplying a control voltage (cntrl) to gate electrodes of the first and second MOS transistors for tuning the resistance of the MOS resistors (84, 86).
9. An integrated circuit having a transconductor circuit as claimed in claim 1.
10. An electronic device having a transconductor circuit as claimed in claim 1.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
1. An apparatus for purifying oil comprising:
an oil inflow pipe into which the oil is introduced;
an oil purification unit that purifies the oil introduced from the oil inflow pipe and has a porous membrane containing carbon nanostructure-metal or -metal oxide composites of a network structure;
an oil outflow pipe through which the oil purified by the oil purification unit is discharged;
an oil heating unit that is installed on any one of the oil inflow pipe and the oil purification unit and heats the oil, and
an oil cooling unit that is installed on the oil outflow pipe and cools the discharged oil,
wherein the porous membrane comprising:
a membrane support having micro or nano-sized pores; and
the carbon nanostructure-metal or -metal oxide composites coated on one surface or both surfaces of the membrane support, wherein the metal of the carbon nanostructure-metal or -metal oxide composites is connected to the surface of the membrane support to form a network structure of carbon nano structure-metal or -metal oxide composites nanoporous film by melting or sintering of the metal,
wherein the porous membrane has a pore size between 10 nm and 500 nm, and
wherein a basis weight of the carbon nanostructure-metal or -metal oxide composites ranges from 0.05 mgcm2 to 10 mgcm2.
2. The apparatus according to claim 1, wherein the porous membrane has a network structure in which metal or metal oxide interconnects carbon nanostructures.
3. A system for purifying oil comprising:
a machine having an oil inlet and an oil outlet;
an oil inflow pipe that is fluid-connected with the oil outlet and introduces the oil discharged from the machine into an oil purification unit;
the oil purification unit that purifies the oil introduced through the oil inflow pipe and includes a porous membrane containing carbon nanostructure-metal or -metal oxide composites of a network structure;
an oil outflow pipe that is fluid-connected with the oil inlet and introduces the oil purified by the oil purification unit into the machine,
a first temperature control unit that is installed on the oil inflow pipe or the oil purification unit and controls the temperature of the oil discharged from the machine; and
a second temperature control unit that is installed on the oil outflow pipe and controls the temperature of the oil introduced into the machine,
wherein the porous membrane, comprising:
a membrane support having micro or nano-sized pores; and
the carbon nanostructure-metal or -metal oxide composites coated on one surface or both surfaces of the membrane support, wherein the metal of the carbon nanostructure-metal or -metal oxide composites is connected to the surface of the membrane support to form a network structure of carbon nanostructure-metal or -metal oxide composites nanoporous film by melting or sintering of the metal,
wherein the porous membrane has a pore size between 10 nm and 500 nm, and
wherein a basis weight of the carbon nanostructure-metal or -metal oxide composites ranges from 0.05 mgcm2 to 10 mgcm2.
4. The system according to claim 3, wherein the porous membrane has a network structure in which metal or metal oxide interconnects carbon nanostructures.