Chopper-stabilized operational transconductance amplifier

A current mirror amplifier characterized by controllably-reversible input and output ports, said current mirror amplifier comprising:

• first, second and third terminals;
• first and second transistors of same conductivity type, each having respective first and second electrodes, having a respective principal conduction path between its first and second electrodes, and having a respective third electrode, the potential difference between the second and third electrodes of each of said first and second transistors controlling the conductance of its said principal conduction path;
• means for connecting the first electrode of said first transistor to said first terminal;
• means for connecting the first electrode of said second transistor to said second terminal;
• means for connecting the second electrode of said first transistor to said third terminal;
• means for connecting the second electrode of said second transistor to said third terminal;
• a first circuit node, the potential at which is applied to the third electrodes of said first and second transistors;
• a first controlled device responsive to a first control signal for selectively applying the potential at the first electrode of said first transistor to said first circuit node;
• a second controlled device responsive to a second control signal for selectively applying the potential at the first electrode of said second transistor to said first circuit node;
• and
• means for applying first and second control signals for selecting only one of said first and second controlled devices to apply potential to said first circuit node during normal operation, whereby, when said first controlled device applies potential to said first circuit node and said second controlled device doe not, a port of said current mirror amplifier between said third and first terminals is conditioned to function as an input port, and a port of said current mirror between said third and second terminals is conditioned to function as an output port, and whereby, when said second controlled device applies potential to said first circuit node and said first controlled device does not, the port of said current mirror amplifier between said third and second terminals is conditioned to function as an input port, and the port of said current mirror amplifier between said third and first terminals is conditioned to function as an input port.

A combination comprising:

• first current supplying means for supplying a first quiescent current having a first signal current superposed thereon;
• second current supplying means for supplying a second quiescent current of substantially the same value of said first quiescent current;
• means for supplying a control signal capable of being in either of first and second conditions;
• a current mirror amplifier having a first terminal to which current supplied by said first current supplying means is applied, having a second terminal to which current supplied by said second current supplying means is applied, having a third terminal connecting for returning current to said first and second current supplying means, having a first port between its said third and first terminals, having a second port between its said third and second terminals, responding to a control signal being in its first condition to select its first port as its input port and its second port as its output port, responding to said control signal being in its second condition to select its second port as its input port and its first port as its output port, and exhibiting a current gain of unity magnitude between its input and output ports;
• and
• means responding to said control signal for selecting an output signal from the output port of said current mirror amplifier, which output signal is responsive to said first signal current but is substantially nonresponsive to said first and second quiescent currents.

A combination comprising:

• first current supplying means for supplying a first quiescent current having a first signal current superposed thereon;
• second current supplying means for supplying a second quiescent current of substantially the same value as said first quiescent current;
• means for supplying a control signal capable of being in either of first and second conditions;
• a current mirror amplifier having an input terminal having a common terminal connected for returning current to said first and second current supplying means, and exhibiting a current gain of unity magnitude between its input and output terminals;
• and
• an electronic switch of double-pole, double-throw type, responding to said first condition of said control signal to provide connections from said first and second current supplying means to provide connections from said first and second current supplying means to said input and output terminals respectively, and responding to said second condition of said control signal to provide connections from said first and second current supplying means to said output and input terminals respectively, which connections when so selectively made offer substantially no intervening impedance as would cause a consequential voltage drop thereacross.

A single-ended-output amplifier comprising:

• an output terminal for said single-ended-output amplifier;
• a push-pull-output amplifier, having an input port for receiving an input signal, and having first and second output terminals for supplying push-pull response currents to said input signal respectively superposed on similar-value quiescent currents;
• means for supplying a control signal capable of being in either of first and second conditions;
• a current mirror amplifier having a first terminal to which the first output terminal of said push-pull-output amplifier connects, having a second terminal to which the second output terminal of said push-pull-output amplifier connects, having a third terminal, having a first port between said first and third terminals, having a second port between said second and third terminals, responding to said control signal being in said first condition to select its first port as its input port and to select its second port as its output port, responding to said control signal being in said second condition to select its second port as its input port and to select its first port as its output port, and exhibiting a current gain of unity magnitude between its input and output ports;
• and
• means responding to said control signal for selectively connecting one of said first and second terminals to said output terminal for said single-ended-output amplifier, said first terminal being selected for such connection responsive to said control signal being in its second condition, and said second terminal being selected for such connection responsive to control signal being in its first condition.

A single-ended-output amplifier comprising:

• an output terminal for said single-ended-output amplifier;
• a push-pull-output amplifier, having an input port for receiving an input signal, and having first and second output terminals for supplying push-pull response currents to said input signal respectively superposed on similar-value quiescent currents;
• means for supplying a control signal capable of being in either of first and second conditions;
• a current mirror amplifier having an input terminal, having an output terminal connected to the output terminal of said single-ended-output amplifier, and exhibiting a current gain of unity magnitude between its input and output terminals;
• and
• an electronic switch of double-pole, double-throw type, responding to said first condition of said control signal to provide connections from said first and second current supplying means to said input and output terminals respectively, and responding to said second condition of said control signal to provide connections from said first and second current supplying means to said output and input terminals respectively, which connections when so selectively made offer substantially no intervening impedance as would permit a consequential voltage drop thereacross.

A differential amplifier comprising:

• first and second power supply terminals for receiving first and second operating voltages respectively;
• first and second enhancement-mode field-effect transistors of a first conductivity type, having respective source, drain and gate electrodes;
• means connecting said first and second field-effect transistors for source-follower operation including connections of their drain electrodes to said first power supply terminal;
• means for applying an input voltage between the gate electrodes of said first and second field-effect transistors, said means for applying being of a type wherein the gate potential of one of said first and second field effect transistor is at times outside the range between said first and second operating voltages;
• third and fourth field effect transistors of a second conductivity type complementary to said first conductivity type, having respective source, drain and gate electrodes;
• means connecting said third and fourth transistors in long-tailed pair configuration, including the following elements of this claim;
• a connection of the gate electrode of said third transistor from the source electrode of said first transistor;
• a connection of the gate electrode of said fourth transistor from the source electrode of said second transistor;
• a fifth field-effect transistor of said second conductivity type, having a source electrode connected to said first power supply terminal, having a drain electrode to which the source electrodes of said third and fourth transistors each connect, and having a gate electrode;
• and
• means biasing the gate electrode of said fifth transistor respective to said first electrode voltage for conditioning said fifth transistor to conduct a tail current of said long-tailed pair configuration.