Transconductance amplifier having low distortion

A circuit, comprising:

• a current source;
• a transconductance amplifier coupled to the current source, the transconductance amplifier having a virtual ground input stage, wherein the virtual ground input stage includes two bipolar junction transistors arranged as a Darlington pair;
• and
• an output stage coupled to the transconductance amplifier, the output stage having a grounded load.

A circuit, comprising:

• a first voltage source;
• a reference resistor coupled to the first voltage source;
• an input stage including
• an operational amplifier coupled to the reference resistor, the operational amplifier having input terminals that are coupled directly to second and third voltage sources, respectively;
• a transistor coupled to be driven by the operational amplifier;
• and
• a bias current source coupled to the transistor and the operational amplifier;
• an output stage including a grounded load resistor;
• and
• a pair of current mirrors, each current mirror coupling the input stage to the output stage.

A transconductance amplifier, comprising:

• an input stage including:
• an amplifier having a first input, a second input, and an output, wherein the first input is coupled to a voltage input node of the transconductance amplifier;
• and
• a transistor having a first conduction terminal coupled to the voltage input node, a control terminal coupled to the output of the amplifier, and a second conduction terminal;
• a first current mirror stage including first, second, third, and fourth transistors, wherein:
• the first transistor has a first conduction terminal coupled to a positive voltage supply node, a second conduction terminal coupled to a first intermediary node, and a control terminal coupled to a second intermediary node;
• the second transistor has a first conduction terminal coupled to the first intermediary node, and a second conduction terminal and a control terminal that are cross-coupled and together coupled, via a current source, to the voltage input node;
• the third transistor has a first conduction terminal coupled to the positive voltage supply node, and a second conduction terminal and a control terminal that are cross-coupled and together coupled to the second intermediary node;
• and
• the fourth transistor has a first conduction terminal coupled to the second intermediary node, a second conduction terminal coupled to a current output node of the transconductance amplifier, and a control terminal coupled to the control terminal of the second transistor;
• and
• a second current mirror stage including first, second, third, and fourth transistors, wherein:
• the first transistor has a first conduction terminal and a control terminal that are cross-coupled and together coupled to the second conduction terminal of the transistor of the input stage, and a second conduction terminal coupled to a third intermediary node;
• the second transistor has a first conduction terminal coupled to the third intermediary node, a second conduction terminal coupled to a negative voltage supply node, and a control terminal coupled to a fourth intermediary node;
• the third transistor has a first conduction terminal coupled to the current output node of the transconductance amplifier, a second conduction terminal coupled to the fourth intermediary node, and a control terminal coupled to the control terminal of the first transistor of the second current mirror stage;
• and
• the fourth transistor has a first conduction terminal and a control terminal that are cross-coupled and together coupled to the fourth intermediary node, and a second conduction terminal coupled to the negative voltage supply node.