Amplifier
An amplifier for a receiver circuit is disclosed. The amplifier has an input node (V in ) and an output node (V out ). It comprises a tunable tank circuit connected to the output node (V out ), a feedback circuit path connected between the output node (V out ) and the input node (V in ), and a tunable capacitor connected between an internal node of the feedback circuit path and a reference-voltage node. A receiver circuit and a communication apparatus is disclosed as well.
1. An amplifier for a receiver circuit, the amplifier having an input node (V in ) and an output node (V out ), comprising
a tunable tank circuit connected to the output node (V out ), wherein the tunable tank circuit is tunable over a frequency range having a plurality of frequency bands, wherein each of the frequency bands has a respective one of a plurality of center frequencies;
a feedback circuit path connected between the output node (V out ) and the input node (V in ); and
a tunable capacitor connected between an internal node of the feedback circuit path and a reference-voltage node, wherein the tunable capacitor is configured to be dynamically tunable over a plurality of capacitance values in correspondence with a concurrent tuning of the tunable tank circuit, wherein each of the capacitance values is configured to cause the amplifier to have a predefined input impedance when the tunable tank circuit is tuned to the respective one of the center frequencies.
2. The amplifier according to claim 1 , wherein the feedback circuit path is a passive circuit.
3. The amplifier according to claim 1 , wherein the feedback circuit path comprises a series connection of at least one resistor and at least one capacitor.
4. The amplifier according to claim 3 , wherein the at least one resistor is tunable.
5. The amplifier according to claim 3 , wherein said at least one capacitor comprises a first capacitor, said at least one resistor comprises a first resistor connected between the output node (V out ) and the first capacitor and a second resistor connected between the first capacitor and the input node (V in ).
6. The amplifier according to claim 5 , wherein the internal node is a node between the first capacitor and the second resistor.
7. The amplifier according to claim 1 , comprising a first transistor in common-source configuration.
8. The amplifier according to claim 7 , comprising a second transistor connected in a cascode configuration between the first transistor and the output node (V out ).
9. A differential amplifier for a receiver circuit, comprising a first and a second amplifier, each according to claim 1 .
10. A receiver circuit comprising an amplifier according to claim 8 .
11. A communication apparatus comprising the receiver circuit according to claim 10 .
12. The communication apparatus according to claim 11 , wherein the communication apparatus is a wireless communication device for a cellular communication network.
13. The communication apparatus according to claim 11 , wherein the communication apparatus is a radio base station for a cellular communication network.
14. A receiver circuit comprising the differential amplifier of claim 9 .