Apparatus and method for transconductance stage with high current response to large signals
First Claim
1. A circuit for providing a current response, comprising:
- a transconductance circuit that is arranged to provide an output current based at least in part on a differential input voltage, wherein the transconductance circuit is arranged to provide the output current at an output current node, and wherein the transconductance circuit includes;
a differential pair including a first transistor and a second transistor;
a tail current source that is coupled to the differential pair;
a first current mirror circuit having at least an input, a first output, and a second output, wherein the input of the first current mirror circuit is coupled to the first transistor, the first output of the current mirror circuit is coupled to an output current node; and
wherein the first current mirror circuit is arranged to provide a first mirror current at the second output of the first current mirror circuit; and
a first output current boost circuit that is coupled to the second output of the first current mirror, wherein the first output current boost circuit is arranged to trip if the first mirror current reaches a threshold, and further arranged to increase the output current if the output current boost circuit is tripped.
1 Assignment
0 Petitions
Accused Products
Abstract
A transconductance stage is provided. The transconductance stage includes a tail current source, a differential pair, and two current mirrors. The input to each of the current mirrors is connected to the drain of a separate one of the transistors in the differential pair. The two current mirrors each have two outputs so that one of the outputs can be used to determine whether the output current exceeds a threshold (e.g. nine-tenths of the tail current). If the source current exceeds the threshold, extra source current is switched in to the output so that output source current is increased. Similarly, if the sink current exceeds the threshold, extra sink current is switched in to the output so that the output sink current is increased. This way, the transconductance stage can supply large output currents in response to a large signal input but maintains low quiescent current for small input signals.
-
Citations
20 Claims
-
1. A circuit for providing a current response, comprising:
a transconductance circuit that is arranged to provide an output current based at least in part on a differential input voltage, wherein the transconductance circuit is arranged to provide the output current at an output current node, and wherein the transconductance circuit includes; a differential pair including a first transistor and a second transistor; a tail current source that is coupled to the differential pair; a first current mirror circuit having at least an input, a first output, and a second output, wherein the input of the first current mirror circuit is coupled to the first transistor, the first output of the current mirror circuit is coupled to an output current node; and
wherein the first current mirror circuit is arranged to provide a first mirror current at the second output of the first current mirror circuit; anda first output current boost circuit that is coupled to the second output of the first current mirror, wherein the first output current boost circuit is arranged to trip if the first mirror current reaches a threshold, and further arranged to increase the output current if the output current boost circuit is tripped. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
-
10. A transconductance circuit that is arranged to provide an output current at an output node, comprising:
-
a differential pair including;
a first transistor having at least a drain, and a second transistor having at least a drain;a tail current source that is coupled to the differential pair; a first current mirror circuit having at least an input, a first output, and a second output, wherein the input of the first current mirror circuit is coupled to the drain of the first transistor; and
wherein the first current mirror circuit is arranged to provide a first mirror current at the second output of the first current mirror circuit;a second current mirror circuit having at least an input, a first output, and a second output, wherein the input of the second current mirror circuit is coupled to the drain of the second transistor;
the second current mirror circuit is arranged to provide a first drain current at the first output of the second current mirror circuit;
the first output of the second current mirror circuit is coupled to the output node; and
wherein the first current mirror circuit is arranged to provide a second mirror current at the second output of the second current mirror circuit;a third current mirror circuit having at least an input and an output, wherein the input of the third current mirror circuit is coupled to the first output of the first current mirror circuit, the output of the third current mirror circuit is coupled to the output node; and
wherein the third current mirror circuit is arranged to provide a first sink current at the output of the third current mirror circuit;a first switch circuit that is arranged to trip if the first mirror current reaches a sink threshold; a first current source circuit that is arranged to provide a second sink current if the first switch circuit is tripped, wherein the first switch circuit is coupled between the first current source circuit and the output node such that, if the first switch circuit is tripped, a total sink current at the output node is substantially given by the first sink circuit plus the second sink circuit; a second switch circuit that is arranged to trip if the second mirror current reaches a source threshold; a fourth current mirror circuit having at least an input and an output, wherein the output of the fourth current mirror circuit is coupled to the output node, and wherein the fourth current mirror circuit is configured to provide a second source current at the output of the fourth current mirror circuit; and a second current source circuit that is arranged to provide a second current source current if the second switch circuit is tripped, wherein the second switch circuit is coupled between the second current source circuit and the output node such that, if the second switch circuit is tripped, a total source current at the output node is substantially given by the first source current plus the second source current. - View Dependent Claims (11, 12, 13, 14, 15, 16)
-
-
17. A method for providing a current response, comprising:
-
providing a tail current to a differential pair, wherein the differential pair includes a first transistor and a second transistor; providing a first sink current to an output current node based, at least in part, on a drain current of the first transistor; providing a first source current to the output current node based, at least in part, on a drain current of the second transistor; determining whether at least one of the first sink current or the first source current exceeds a threshold; and if the at least one of the first sink current or the first source current exceeds the threshold, switching in an additional current to the output current node increase the magnitude of output current provided at the current output node. - View Dependent Claims (18, 19, 20)
-
Specification