Circuit having an amplifier stage and a current mirror loop or stability network

1 . A circuit, comprising:

an amplifier stage comprising a first positive amplifier branch, a second positive amplifier branch, a first negative amplifier branch, and a second negative amplifier branch, the amplifier stage having current flow paths therethrough cascaded in a first flow line for a first core current for the amplifier stage between a supply node and a ground node, wherein the first positive amplifier branch and the first negative amplifier branch have respective input nodes configured to receive an input signal applied therebetween, and wherein the second positive amplifier branch and the second negative amplifier branch have current flow paths therethrough cascaded in a second flow line for a second core current between the supply node and the ground node; and

a current mirror loop coupled to the respective input nodes of the first positive amplifier branch, the second positive amplifier branch, the first negative amplifier branch, and the second negative amplifier branch, wherein the current mirror loop provides an adjustable high-impedance bias source for the first core current for the amplifier stage.

2 . The circuit of claim 1 , wherein the amplifier stage further comprises a cascode amplifier branch coupled between the first positive amplifier branch and the first negative amplifier branch.

3 . The circuit of claim 1 , wherein the current mirror loop comprises:

a bias transistor pair comprising first and second bias transistors having current flow paths therethrough cascaded in a bias current flow line between the supply node and the ground node, the first and second bias transistors having control terminals coupled to the respective input nodes of the first positive amplifier branch and the first negative amplifier branch; and

a diode-connected reference bias transistor having a control terminal coupled in a current mirror arrangement with a control terminal of the second bias transistor.

4 . The circuit of claim 1 , further comprising a stability network having a gain bandwidth range, the stability network having a first input coupled to an output signal of the amplifier stage and a second input coupled to receive an output voltage setting signal, wherein the amplifier stage is configured to short-circuit the output signal from the amplifier stage within the gain bandwidth range based on the output voltage setting signal.

5 . A method of operating the circuit of claim 4 , the method comprising:

operating the current mirror loop to provide an adjustable high-impedance bias source for the first core current for the amplifier stage;

receiving an output voltage setting signal by the stability network; and

based on the output voltage setting signal, controlling the amplifier stage to short-circuit an output signal from the amplifier stage within the gain bandwidth range.

6 . A variable-gain amplifier, comprising:

the circuit of claim 1 ;

an input impedance circuit branch; and

a variable-impedance feedback circuit branch;

wherein the respective input nodes of the amplifier stage are configured to receive the input signal applied therebetween via the input impedance circuit branch;

wherein the amplifier stage includes an output node configured to provide an output signal that is a replica of the input signal having a variable gain applied thereto;

wherein the variable-impedance feedback circuit branch is configured to couple the output node to the respective input nodes; and

wherein the gain applied to the input signal is a function of an impedance value of the variable-impedance feedback circuit branch.

7 . The variable-gain amplifier of claim 6 , wherein the input impedance circuit branch comprises a variable-impedance input impedance network, and wherein the gain applied to the input signal is a function of a ratio of an impedance value of the variable-impedance feedback circuit branch and an impedance value of the variable-impedance input impedance network.

8 . A device comprising:

the variable-gain amplifier according to claim 6 ;

a signal source configured to provide the input signal; and

an electrical load coupled to the output node to receive the output signal.

9 . A circuit, comprising:

an amplifier stage comprising a first positive amplifier branch, a second positive amplifier branch, a first negative amplifier branch, and a second negative amplifier branch, the amplifier stage having current flow paths therethrough cascaded in a first flow line for a first core current for the amplifier stage between a supply node and a ground node, wherein the first positive amplifier branch and the first negative amplifier branch have respective input nodes configured to receive an input signal applied therebetween, and wherein the second positive amplifier branch and the second negative amplifier branch have current flow paths therethrough cascaded in a second flow line for a second core current between the supply node and the ground node; and

a stability network having a gain bandwidth range, the stability network having a first input coupled to an output signal of the amplifier stage and a second input coupled to receive an output voltage setting signal, wherein the amplifier stage is configured to short-circuit the output signal from the amplifier stage within the gain bandwidth range based on the output voltage setting signal.

10 . The circuit of claim 9 , wherein the amplifier stage further comprises a cascode amplifier branch coupled between the first positive amplifier branch and the first negative amplifier branch.

11 . The circuit of claim 9 , wherein the stability network has an output node coupled to a node between the first positive amplifier branch and the first negative amplifier branch in the amplifier stage or to a control node of one of the first positive amplifier branch and the first negative amplifier branch.

12 . The circuit of claim 11 , wherein the stability network comprises a low-pass filter network that provides the gain bandwidth range and has an output node, wherein the output node of the low-pass filter network is coupled to the node between the first positive amplifier branch and the first negative amplifier branch via a decoupling gain stage or is coupled to the control node of the one of the first positive amplifier branch and the first negative amplifier branch in the amplifier stage.

13 . The circuit of claim 11 , wherein the amplifier stage further comprises:

a second stability network;

wherein the stability network has an output node coupled to a node between the first positive amplifier branch and the first negative amplifier branch or the control node of the one of the first positive amplifier branch and the first negative amplifier branch; and

wherein the second stability network has an output node coupled to a node between the second positive amplifier branch and the second negative amplifier branch or to a control node of one of the second positive amplifier branch and the second negative amplifier branch.

14 . A variable-gain amplifier, comprising:

the circuit of claim 9 ;

an input impedance circuit branch; and

a variable-impedance feedback circuit branch;

wherein the respective input nodes of the amplifier stage are configured to receive the input signal applied therebetween via the input impedance circuit branch;

wherein the amplifier stage includes an output node configured to provide the output signal, which is a replica of the input signal having a variable gain applied thereto;

wherein the variable-impedance feedback circuit branch is configured to couple the output node to the respective input nodes; and

wherein the gain applied to the input signal is a function of an impedance value of the variable-impedance feedback circuit branch.

15 . The variable-gain amplifier of claim 14 , wherein the input impedance circuit branch comprises a variable-impedance input impedance network and wherein the gain applied to the input signal is a function of a ratio of an impedance value of the variable-impedance feedback circuit branch and an impedance value of the variable-impedance input impedance network.

16 . A device comprising:

the variable-gain amplifier according to claim 14 ;

a signal source configured to provide the input signal; and

an electrical load coupled to the output node to receive the output signal.

17 . A method of operating an amplifier circuit that includes an amplifier stage and a current mirror loop, wherein the amplifier stage comprises a first positive amplifier branch, a second positive amplifier branch, a first negative amplifier branch, and a second negative amplifier branch, the first positive amplifier branch and the first negative amplifier branch having current flow paths therethrough cascaded in a first flow line for a first core current for the amplifier stage, the first flow line extending between a supply node and ground node, wherein the second positive amplifier branch and the second negative amplifier branch have current flow paths therethrough cascaded in a second flow line for a second core current between the supply node and the ground node, wherein the first positive amplifier branch and the first negative amplifier branch have respective input nodes configured to receive an input signal applied therebetween, and wherein the current mirror loop is coupled to the respective input nodes of the first positive amplifier branch, the second positive amplifier branch, the first negative amplifier branch, and the second negative amplifier branch, the method comprising:

operating the current mirror loop to provide an adjustable high-impedance bias source for the first core current for the amplifier stage.

18 . A method of operating an amplifier circuit that includes an amplifier stage and a stability network having a gain bandwidth range, wherein the amplifier stage comprises a first positive amplifier branch, a second positive amplifier branch, a first negative amplifier branch, and a second negative amplifier branch, the first positive amplifier branch and the second negative amplifier branch having current flow paths therethrough cascaded in a first flow line for a first core current for the amplifier stage, the flow line extending between a supply node and a ground node, wherein the second positive amplifier branch and the second negative amplifier branch have current flow paths therethrough cascaded in a second flow line for a second core current between the supply node and the ground node, wherein the first positive amplifier branch and the first negative amplifier branch have respective input nodes configured to receive an input signal applied therebetween, and wherein the stability network to an output of the amplifier stage, the method comprising:

receiving an output voltage setting signal by the stability network; and

based on the output voltage setting signal, controlling the amplifier stage to short-circuit an output signal from the amplifier stage within the gain bandwidth range.

19 . The method of claim 18 , wherein the stability network comprises a low-pass filter network that provides the gain bandwidth range and has an output node, wherein the output node of the low-pass filter network is coupled to the node between the first positive amplifier branch and the first negative amplifier branch via a decoupling gain stage or is coupled to the control node of one of the first positive amplifier branch and the first negative amplifier branch in the amplifier stage.

20 . The method of claim 17 , wherein the amplifier circuit further comprises a stability network having a gain bandwidth range, the stability network having a first input coupled to an output signal of the amplifier stage and a second input coupled to receive an output voltage setting signal, wherein the amplifier stage is configured to short-circuit the output signal from the amplifier stage within the gain bandwidth range based on the output voltage setting signal, the method further comprising:

operating the current mirror loop to provide an adjustable high-impedance bias source for the first core current;

receiving an output voltage setting signal by the stability network; and

based on the output voltage setting signal, controlling the amplifier stage to short-circuit an output signal from the amplifier stage within the gain bandwidth range.