Rail to rail class AB output for an amplifier

An output stage of an amplifier, comprising:

• an input node;
• an output node;
• a source transistor connected between a supply rail and the output node and having a first control terminal;
• a sinking transistor connected between the output node and a ground rail and having a second control terminal;
• a control transistor coupled between the first and second control node and defining a path with an intermediate node, the control transistor having a third control terminal;
• an input transistor coupled between the supply rail and the ground rail and having a fourth control terminal that is connected to the input node, the input transistor coupling the input node to the intermediate node;
• and
• a biasing circuit coupled between the supply rail and the ground rail to supply a bias to the third control terminal.

An output stage for an operational amplifier circuit, comprising:

• an output section comprising a class AB complementary pair of transistors connected to an output node;
• a biasing section comprising a bias transistor coupled between control terminals of the complementary pair of transistors;
• a drive section receiving at its input a drive voltage and operating:
• in response to decreasing drive voltage by drawing current from the control terminal of a first one of the complementary pair of transistors to allow current to be supplied to the output node while turning off the bias transistor and preventing a second one of the complementary pair of transistors from sinking current from the output node;
• and
• in response to increasing drive voltage by supplying current toward the control terminal of the first one of the complementary pair of transistors to prevent current from being supplied to the output node while turning on the bias transistor and allowing the second one of the complementary pair of transistors to sink current from the output node.

An output stage for an operational amplifier circuit, comprising:

• an output section comprising a class AB complementary pair of transistors connected to an output node;
• a biasing section comprising a bias transistor coupled between control terminals of the complementary pair of transistors;
• a drive section receiving at its input a drive voltage and operating:
• in response to decreasing drive voltage by drawing current from the control terminal of a second one of the complementary pair of transistors to prevent the sinking of current from the output node while turning on the bias transistor and allowing a first one of the complementary pair of transistors to supply current to the output node;
• and
• in response to increasing drive voltage by supplying current toward the control terminal of the second one of the complementary pair of transistors to allow sinking of current from the output node while turning off the biasing transistor to prevent the first one of the complementary pair of transistors from supplying current to the output node.