Wideband amplifier
A wideband amplifier includes an input matching network for matching a transconductor stage to an input impedance and includes an output matching network for matching the transconductor stage to an output impedance. Both the input and output matching networks each includes a parallel LC tank circuit arranged in parallel with a series LC tank circuit. The tank circuit arrangements configure the input and output matching networks to be resonant at a first frequency, a midrange frequency that is greater than the first frequency, and a second frequency that is greater than the midrange frequency to provide wideband matching.
1 . An amplifier, comprising:
a transconductor stage including a transconductor stage output node, the transconductor stage being configured to amplify an input signal; and
an output matching network including:
a first inductor having a first terminal coupled to the transconductor stage output node;
an output transformer including a first coil electromagnetically coupled to a second coil, the first coil having a first terminal coupled to a reference voltage node and a second terminal coupled to a second terminal of the first inductor, the second coil being coupled to an amplifier output node; and
a first capacitor coupled between the second terminal of the first inductor and the reference voltage node.
2 . The amplifier of claim 1 , wherein the first capacitor is a variable capacitor, and wherein the reference voltage node is a power supply node for a power supply voltage.
3 . The amplifier of claim 1 , wherein the output matching network further includes a resistor coupled between the second terminal of the first inductor and the reference voltage node.
4 . The amplifier of claim 3 , wherein the resistor is a variable resistor.
5 . The amplifier of claim 1 , wherein the output matching network further includes:
a second capacitor coupled between the transconductor stage output node and the reference voltage node.
6 . The amplifier of claim 5 , wherein the output matching network further includes:
a resistor coupled between the transconductor stage output node and the reference voltage node.
7 . The amplifier of claim 6 , wherein the second capacitor is a variable capacitor and the resistor is a variable resistor.
8 . The amplifier of claim 1 , wherein an inductance of the first coil is greater than an inductance of the second coil.
9 . The amplifier of claim 1 , wherein the transconductor stage comprises:
a first transconductor transistor, wherein an input node of the transconductor stage is formed by a gate of the first transconductor transistor; and
a first cascode transistor having a source coupled to a drain of the first transconductor transistor and having a drain coupled to the transconductor stage output node.
10 . The amplifier of claim 9 , wherein the transconductor stage further comprises:
a second transconductor transistor, wherein the input node of the transconductor stage is further formed by a gate of the second transconductor transistor, and
a second cascode transistor having a source coupled to a drain of the second transconductor transistor and having a drain coupled to the transconductor stage output node.
11 . The amplifier of claim 9 , further comprising:
a degeneration inductor coupled between a source of the first transconductor transistor and ground.
12 . The amplifier of claim 10 , further comprising:
a bias generator configured to generate a first gate bias voltage for a gate of the first cascode transistor and configured to generate a second gate voltage for a gate of the second cascode transistor; and
a controller configured to control the bias generator to adjust the first gate bias voltage and the second gate bias voltage to control a gain of the transconductor stage.
13 . The amplifier of claim 1 , wherein the output matching network further comprises a second capacitor coupled between the second coil and the amplifier output node.
14 . The amplifier of claim 1 , further comprising:
an input matching network coupled between an amplifier input node and an input node of the transconductor stage.
15 . The amplifier of claim 14 , wherein the input matching network includes a second inductor coupled between ground and the amplifier input node; a capacitor having a first terminal and a second terminal, wherein the second terminal of the capacitor is coupled to the input node of the transconductor stage; and a third inductor coupled between the amplifier input node and the first terminal of the capacitor.
16 . The amplifier of claim 1 , wherein the amplifier comprises a low-noise amplifier integrated within a receiver comprising:
a mixer coupled to the amplifier output node;
an analog-to-digital converter; and
a filter coupled between an output node of the mixer and an input node to the analog-to-digital converter.
17 . The amplifier of claim 1 , further comprising:
a plurality of electrostatic discharge diodes coupled to the amplifier output node.
18 . The amplifier of claim 1 , further comprising:
a plurality of electrostatic discharge diodes coupled to an amplifier input node of the amplifier.
19 . An amplification method, comprising:
transconducting a first input voltage signal through a transconductor stage having an output capacitance to form a first output current signal; and
driving the first output current signal into a parallel combination of a series inductor-capacitor tank circuit and a first parallel inductor-capacitor tank circuit, wherein the series inductor-capacitor tank circuit includes the output capacitance and an inductor coupled between a first coil of an output transformer and an output node of the transconductor stage and the first parallel inductor-capacitor tank circuit includes a capacitor arranged in parallel with the first coil of the output transformer, to cause both the series inductor-capacitor tank circuit and the first parallel inductor-capacitor tank circuit to be resonant at a midrange frequency to match an impedance of an amplifier output node at the midrange frequency to an output resistance of the transconductor stage, wherein the midrange frequency is greater than a first frequency and less than a second frequency.
20 . The method of claim 19 , wherein driving the first output current signal into the parallel combination of the series inductor-capacitor tank circuit and the first parallel inductor-capacitor tank circuit further comprises:
causing the series inductor-capacitor tank circuit to function as a short circuit.
21 . The method of claim 19 , further comprising:
transconducting a second input voltage signal through the transconductor stage to form a second output current signal; and
driving the second output current signal into the parallel combination of the series inductor-capacitor tank circuit and the first parallel inductor-capacitor tank circuit to cause a combination of the first coil and the output capacitance to function as a second parallel inductor-capacitor tank circuit that is resonant at the first frequency to match an impedance of the amplifier output node at the first frequency to a product of the output resistance of the transconductor stage and a quality factor of the series inductor-capacitor tank circuit.
22 . The method of claim 21 , wherein driving the second output current signal into the parallel combination of the series inductor-capacitor tank circuit and the first parallel inductor-capacitor tank circuit further comprises:
causing the second parallel inductor-capacitor tank circuit to function as an open circuit.
23 . The method of claim 21 , further comprising:
transconducting a third input voltage signal through the transconductor stage to form a third output current signal; and
driving the third output current signal into the parallel combination of the series inductor-capacitor tank circuit and the first parallel inductor-capacitor tank circuit to cause a combination of the capacitor and the inductor to function as a third parallel inductor-capacitor tank circuit that is resonant at the second frequency to match an impedance of the amplifier output node at the second frequency to a product of the output resistance of the transconductor stage and the quality factor of the series inductor-capacitor tank circuit.
24 . The method of claim 23 , wherein driving the third output current signal into the parallel combination of the series inductor-capacitor tank circuit and the first parallel inductor-capacitor tank circuit further comprises:
causing the third parallel inductor-capacitor tank circuit to function as an open circuit.
25 . An amplifier, comprising:
a transconductor stage including a first transconductor transistor; and
an input matching network including a first inductor coupled between an amplifier input node and ground, a second inductor having a first terminal coupled to the amplifier input node, a capacitor coupled between a second terminal of the second inductor and a gate of the first transconductor transistor, and a degeneration inductor coupled to a source of the first transconductor transistor, wherein a combination of an inductance of the second inductor, an inductance of the degeneration inductor, and a parasitic gate-to-source capacitance of the first transconductor transistor is configured to form a series inductor-capacitor (LC) tank circuit that is resonant at a first frequency, and wherein a combination of a capacitance of the amplifier input node and an inductance of the first inductor is configured to form a parallel LC tank circuit that is resonant at the first frequency.
26 . The amplifier of claim 25 , wherein the input matching network further comprises:
a first switch;
a variable capacitor coupled through the first switch to the amplifier input node; and
a first variable resistor coupled through the first switch to the amplifier input node.
27 . The amplifier of claim 26 , wherein the input matching network further comprises:
a second switch; and
a second variable resistor coupled through the second switch to the second terminal of the second inductor.
28 . The amplifier of claim 25 , wherein the transconductor stage is included in an integrated circuit, and wherein the first inductor, the capacitor, and degeneration inductor are also included in the integrated circuit.
29 . The amplifier of claim 25 , wherein the transconductor stage is included in an integrated circuit, and wherein the first inductor is a discrete component separate from the integrated circuit.
30 . The amplifier of claim 25 , wherein the transconductor stage further includes:
a transconductor stage output node; and
a first cascode transistor coupled between the first transconductor transistor and the transconductor stage output node.
31 . The amplifier of claim 30 , wherein the transconductor stage further includes:
a second transconductor transistor having a gate coupled through the capacitor to the second terminal of the second inductor and having a source coupled to the degeneration inductor; and
a second cascode transistor coupled between the second transconductor transistor and the transconductor stage output node.
32 . The amplifier of claim 31 , further comprising:
a controller configured to selectively control a gate voltage of the first cascode transistor and a gate voltage of the second cascode transistor to adjust a gain of the transconductor stage.
33 . The amplifier of claim 30 , further comprising:
an amplifier output node; and
an output matching network including an output transformer having a first coil electromagnetically coupled to a second coil, the second coil being coupled to the amplifier output node, the matching output network further including a third inductor coupled between the transconductor stage output node and the first coil.
34 . The amplifier of claim 33 , wherein the first coil is coupled between a power supply node for a power supply voltage and the third inductor, and wherein the output matching network further includes a variable capacitor coupled between the power supply node and the third inductor.
35 . The amplifier of claim 1 , wherein the first inductor and a capacitance of the transconductor stage form a series inductor-capacitor tank circuit, wherein the first coil and the first capacitor form a parallel inductor-capacitor tank circuit, wherein both the series inductor-capacitor tank circuit and the parallel inductor-capacitor tank circuit are configured to be resonant at a midrange frequency, wherein the midrange frequency is greater than a first frequency and less than a second frequency associated with a bandwidth of the amplifier.
36 . An amplifier, comprising:
a transconductor stage including a transconductor stage output node, the transconductor stage being configured to amplify an input signal;
an output matching network including:
a first inductor having a first terminal coupled to the transconductor stage output node;
an output transformer including a first coil electromagnetically coupled to a second coil, the first coil being coupled between a reference voltage node and a second terminal of the first inductor, the second coil being coupled to an amplifier output node; and
a first capacitor coupled between the second terminal of the first inductor and the reference voltage node; and
an input matching network coupled between an amplifier input node and an input node of the transconductor stage, wherein the input matching network includes a second inductor coupled between ground and the amplifier input node; a capacitor having a first terminal and a second terminal, wherein the second terminal of the capacitor is coupled to the input node of the transconductor stage; and a third inductor coupled between the amplifier input node and the first terminal of the capacitor.