Apparatus providing a substantially equal transconductance ratio and method

An apparatus comprising:

• a master terminal for receiving a master signal;
• a network coupled to said master terminal for deriving a first control signal depending on said master signal;
• a first current mirror providing a first current to a first node and a second current to a second node, said first and second currents being related by a substantially constant factor, said first current mirror deriving a second control signal from said first current;
• a transistor arrangement with first, second, third, and fourth transistors, each transistor having first and second main electrodes and a control electrode, first main electrodes of said first and fourth transistor coupled to said first node, first main electrodes of said second and third transistor coupled to said second node, said second main electrodes of said first and third transistors coupled to a first reference line, second main electrodes of said second and fourth transistors coupled to a second reference line, said control electrodes of said first and second transistor receiving said first control signal and said control electrodes of said third and fourth transistors receiving said second control signal.

An apparatus comprising:

• an input unit receiving a master signal and providing a first control signal;
• a current mirror providing a current I.sub.A and a current I.sub.B ;
• a first node splitting current I.sub.A into a current I.sub.12 and a current I.sub.23 :
• I.sub.A .apprxeq.I.sub.12 +I.sub.23 ;
• a second node splitting current I.sub.B into a current I.sub.22 and a current I.sub.13 :
• I.sub.B .apprxeq.I.sub.22 +I.sub.23 ;
• first and second transistors conducting current I.sub.22 and current I.sub.12, respectively, to a reference line, said first and second transistors being controlled by said first control signal which determines a first common transconductance of said first and second transistors;
• third and fourth transistors conducting current I.sub.23 and current I.sub.13, respectively, to said reference line, said third and fourth transistors being controlled by a second control signal derived from current I.sub.13 such that a second common transconductance of said third and fourth transistors substantially equals said first transconductance, a transconductance drift causing a current drift of a current difference between current I.sub.23 and current I.sub.13.

A method for regulating the transconductances in first, second, third, and fourth transistors, said method comprising the steps of:

• receiving a master signal;
• deriving a first control signal from said master signal;
• distributing a first current to said first transistor as a first partial current and to said second transistor as a second partial current and distributing a second current to said third transistor as a third partial current and to said fourth transistor as a fourth partial current, thereby controlling said first and fourth transistors by said first control signal and controlling said second and third transistors by a second control signal derived from said third partial current, such that a transconductance ratio between said first and fourth transistors and said second and third transistors is established;
• monitoring changes in said transconductance ratio through changes of said third current and providing an intermediate signal;
• and
• providing a feedback by modifying said first control signal according to said intermediate signal.

An apparatus comprising:

• first, second and third reference lines, wherein a voltage source is coupled between said second and third reference lines;
• a current mirror coupled to said first reference line and to first and second nodes;
• first, second, third and fourth transistors, each having first and second electrodes, said first and second transistors having said first electrodes coupled to said first node, said third and fourth transistors having said first electrodes coupled to said second node, said second and third transistors having said second electrodes coupled to said second reference line, and said first and fourth transistors having said second electrodes coupled to said third reference line, wherein
• said current mirror providing that first and second currents between said first reference line and said first and second nodes, respectively, have substantially equal magnitudes so that transconductances of said first, second, third and fourth transistors are substantially equal and that changes in said transconductances are expressed by changes in currents through said transistors.