Low noise amplifier
An embodiment of an LNA includes a voltage input, a voltage output, an input transistor connected as a source follower with a current source at the drain and source nodes of the input transistor, an input resistor connected between the source follower source node and signal ground, a gain boosting transistor with the gate connected to the input transistor drain node, wherein the source node is connected to ground and the drain node is connected through a load resistor to the input transistor source node. Such an LNA provides substantial improvement in power efficiency by adapting an output stage of the LNA to reuse the supply current of the input transistors to the LNA through a load resistor.
1. A low noise amplifier (LNA), comprising:
a voltage input;
a voltage output;
an input transistor comprising drain and source nodes, wherein the input transistor is connected as a source follower;
an input resistor connected between the source follower source node and a signal ground;
a gain boosting transistor with the gate connected to the drain node of the input transistor; and
wherein a source node of the gain boosting transistor is connected to ground and a drain node of the gain boosting transistor is connected through a load resistor to the input transistor source node.
2. The LNA of claim 1 , wherein the voltage output is the drain node of the gain boosting transistor.
3. The LNA of claim 1 implemented as a differential circuit wherein the input resistor is connected between a non-inverting input source follower source node and an inverting input source follower source node.
4. A multi stage amplifier having the LNA of claim 1 as an input amplifier.
5. A low noise amplifier (LNA), comprising:
a voltage input;
a voltage output;
an input transistor comprising a drain node and a source node, the input transistor connected as a source follower;
an input resistor connected between the source node of the input transistor and a signal ground;
a gain boosting transistor with a gate connected to the drain node of the input transistor; and
wherein the source node of the gain boosting transistor is connected to ground and the drain node of the gain boosting transistor is connected through a load resistor to the source node of the input transistor.
6. The LNA of claim 5 , wherein the voltage output is the drain node of the gain boosting transistor.
7. The LNA of claim 6 implemented as a differential circuit wherein the input resistor is connected between a non-inverting input source follower source node and an inverting input source follower source node.
8. A multi stage amplifier having the LNA of claim 5 as an input amplifier.
9. The LNA of claim 1 , wherein a current source is operatively coupled to the drain and source nodes of the input transistor.
10. The LNA of claim 5 , wherein a current source is operatively coupled to the drain and source nodes of the input transistor.
11. A low noise amplifier (LNA), comprising:
a voltage input;
a voltage output;
an input transistor;
an input resistor connected between a source node of the input transistor and a signal ground;
a load resistor;
a gain boosting transistor with a gate connected to a drain node of the input transistor, a source node connected to ground, and a drain node connected through the load resistor to the source node of the input transistor, such that the gain boosting transistor reuses supply current of the input transistor through the load resistor.
12. The LNA of claim 11 , wherein the voltage output is the drain node of the gain boosting transistor.
13. The LNA of claim 11 implemented as a differential circuit wherein the input resistor is connected between a non-inverting input source follower source node and an inverting input source follower source node.
14. A multi stage amplifier having the LNA of claim 11 as an input amplifier.
15. The LNA of claim 11 , wherein the input transistor is connected as a source follower with a current source operatively coupled to the drain and source nodes of the input transistor.