Apparatus and method for a turn around stage having reduced power consumption, Class AB behavior, low noise and low offset

An apparatus for a circuit with an input voltage range that is independent of the output voltage range, comprising:

• (a) an input stage adapted for receiving an input signal, a first current source is coupled to an emitter of a first transistor and an emitter of a second transistor, a current provided by the first current source is evenly split between the emitters of the first and second transistors when a polarity of the input signal is equal, and the current provided by the first current source flows through one of the first and second transistors when one of the first and second transistors is activated by an unequal polarity of the input signal and the other of the first and second transistors is deactivated by the unequal polarity of the input signal;
• (b) a turn around stage that outputs an output signal when the polarity of the input signal is unequal, a second current source is coupled to a collector of a third transistor and a third current source is coupled to a collector of a fourth transistor, the flow of the current through the one of the first and second transistors that is activated causes one of the third and fourth transistors to be deactivated and another one of the third and fourth transistors to be activated and conduct an output current from one of the second and third current sources that is substantially larger than another current that flows through the other one of the third and fourth transistors that is deactivated;
• and
• (c) a bias circuit for separately providing a floating bias for the operation of the third and fourth transistors, a base and a collector of a fifth transistor is coupled to a base of the third transistor and a fourth current source and an emitter of the fifth transistor is cross coupled to an emitter of the fourth transistor, a base and a collector of a sixth transistor is coupled to a base of the fourth transistor and the fourth current source and an emitter of the sixth transistor is cross coupled to an emitter of the third transistor, wherein the cross coupling of the emitters of the fifth and sixth transistors reduces noise and power consumption of the circuit.

An apparatus for a circuit with an input voltage range that is independent of the output voltage range, comprising:

• (a) means for receiving an input signal, a current provided by a first current source flows substantially through one of a first switch and a second switch when a polarity of one of the first and second switches is activated by an unequal polarity of the input signal and the other one of the first and second switches is deactivated by the unequal polarity of the input signal;
• (b) means for outputting an output signal when the polarity of the input signal is unequal, the flow of the current through the one of the first and second switches that is activated causes one of a third switch and a fourth switch to be deactivated and the other one of the third and fourth switches to be activated and conduct an output current that is substantially larger than another current that flows through the one of the third and fourth switches that is deactivated;
• and
• (c) means for separately providing a floating bias for the operation of the third and fourth switches, a fifth switch biases the operation of the third switch and an emitter of the fifth switch is cross coupled to an emitter of the fourth switch, a sixth switch biases the operation of the fourth switch and an emitter of the sixth switch is cross coupled to an emitter of the third switch, wherein the cross coupling of the emitters of the fifth and sixth switches reduces noise and power consumption of the circuit.

A method for providing an input voltage range that is independent of the output voltage range in a circuit, comprising:

• (a) receiving an input signal, a current provided by a first current source flows substantially through one of a first switch and a second switch when a polarity of one of the first and second switches matches an unequal polarity of the input signal;
• (b) outputting an output signal when the polarity of the input signal is unequal, the flow of the current through the one of the first and second switches that is activated causes one of a third switch and a fourth switch to be deactivated and the other one of the third and fourth switches to be activated and conduct an output current that is substantially larger than another current that flows through the one of the third and fourth switches that is deactivated;
• and
• (c) separately providing a floating bias for the operation of the third and fourth switches, a fifth switch biases the operation of the third switch and an emitter of the fifth switch is cross coupled to an emitter of the fourth switch, a sixth switch biases the operation of the fourth switch and an emitter of the sixth switch is cross coupled to an emitter of the third switch, wherein the cross coupling of the emitters of the fifth and sixth switches reduces noise and power consumption of the circuit.