Multi-path broadband amplifier

1. An amplifier device having an extended total bandwidth, the amplifier device comprising:

a DC coupled amplifier having a broad bandwidth; and

a plurality of first low noise amplifiers connected in series with one another and connected in parallel with at least a portion of the DC coupled amplifier, the plurality of first low noise amplifiers having a first narrow bandwidth and a center frequency higher than a high end frequency of the broad bandwidth,

wherein the extended total bandwidth of the amplifier device comprises a combination of the broad bandwidth and the first narrow bandwidth, and

wherein the broad bandwidth of the DC coupled amplifier provides at least 50 percent of the extended total bandwidth.

2. The amplifier device of claim 1 , wherein the DC coupled amplifier comprises a high frequency pick-off node, and an input of one of the plurality of first low noise amplifiers is connected to the high frequency pick-off node of the DC coupled amplifier.

3. The amplifier device of claim 1 , further comprising:

an input node configured to receive an input voltage signal, wherein an input of the DC coupled amplifier and an input of one of the plurality of first low noise amplifiers is connected to the input node.

4. The amplifier device of claim 1 , wherein the number of first low noise amplifiers is determined such that amplitude and phase of a narrow bandwidth signal output by the plurality of first low noise amplifiers matches amplitude and phase of a broadband signal output by the DC coupled amplifier.

5. The amplifier device of claim 4 , wherein an overall magnitude response of an output signal of the amplifier device is substantially flat, and an overall phase response of the output signal of the amplifier device is linear or transitions smoothly.

6. The amplifier device of claim 4 , wherein the DC coupled amplifier comprises a delay element configured to adjust the phase of the broadband signal output by the DC coupled amplifier.

7. The amplifier device of claim 1 , further comprising:

a plurality of second low noise amplifiers connected in series with one another and connected in parallel with the plurality of first low noise amplifiers, the plurality of second low noise amplifiers having a second narrow bandwidth,

wherein the extended bandwidth of the amplifier device comprises a combination of the broad bandwidth and the first and second narrow bandwidths.

8. The amplifier device of claim 1 , wherein a gain of the plurality of first low noise amplifiers is based, in part, on the number of first low noise amplifiers connected in series.

9. The amplifier device of claim 1 , wherein the DC coupled amplifier is one of a single-ended amplifier and a differential amplifier.

10. The amplifier device of claim 9 , wherein each of the first low noise amplifiers is one of a single-ended amplifier and a differential amplifier.

11. The amplifier device of claim 1 , wherein the broad bandwidth of the DC coupled amplifier is in a range of about 30 GHz to about 50 GHz, and the narrow bandwidth of the plurality of low noise amplifiers is in a range of about 4 GHz to about 40 GHz.

12. The amplifier device of claim 1 , wherein each of the plurality of first low noise amplifiers comprises:

a first transistor having a base corresponding to an input of the first low noise amplifier; and

a second transistor having a base connected to a bias voltage, an emitter connected to a collector of the first transistor, and a collector connected to ground via a load inductor and connected to an output of the first low noise amplifier via a coupling capacitor.

13. The amplifier device of claim 10 , further comprising:

an output stage connected in series with the plurality of first low noise amplifiers, the output stage comprising:

a third transistor having a base connected to the output of a first low noise amplifier; and

a fourth transistor having a base connected to a bias voltage, an emitter connected to a collector of the third transistor, and a collector comprising an output to be combined with an output of the DC coupled amplifier.

14. An amplifier device, comprising:

a first path including a DC coupled amplifier, the first path having a first path delay;

a second path connected in parallel with the first path and including an AC coupling capacitor connected in series with at least one high frequency amplifier, the second path having a second delay that is substantially the same as the first delay;

a third path including at least one high frequency amplifiers connected in parallel with the at least one high frequency amplifier of the second path, the third path having a third delay that is substantially the same as the first and second delays; and

a summing node configured to combine a first signal output by the first path and a second signal output by the second path to provide an output signal of the amplifier device,

wherein a total bandwidth of the amplifier device comprises a combination of a broad bandwidth of the DC coupled amplifier and a narrow bandwidth of the at least one high frequency amplifier, and

wherein the at least one high frequency amplifier has a center frequency higher than a high end frequency of the broad bandwidth of the DC coupled amplifier.

15. The amplifier device of claim 14 , wherein the broad bandwidth of the DC coupled amplifier provides at least 50 percent of the total bandwidth of the amplifier device.

16. An amplifier having an extended bandwidth, the amplifier device comprising:

a first path comprising a DC coupled amplifier having a broad bandwidth; and

a second path comprising an AC coupling capacitor, connected to a high frequency pick-off node of the DC coupled amplifier, and at least one first low noise amplifier and an output stage connected between the coupling capacitor and a summing node, the at least one first low noise amplifier having a first narrow bandwidth and a center frequency higher than a high end frequency of the broad bandwidth of the DC coupled amplifier,

wherein an output of the DC coupled amplifier is connected to one of the output stage and the summing node,

wherein the extended bandwidth of the amplifier device at the summing node comprises a combination of the broad bandwidth and the first narrow bandwidth, and

wherein the number of first low noise amplifiers is determined such that amplitude and phase of a signal output by the second path matches amplitude and phase of a signal output by the first path at the summing node.

17. The amplifier device of claim 16 , further comprising:

a third path comprising at least one second low noise amplifier connected between the coupling capacitor and the summing node in parallel with the at least one first low noise amplifier, the at least one second low noise amplifier having a second narrow bandwidth substantially the same as the first narrow bandwidth,

wherein the extended bandwidth of the amplifier device comprises a combination of the broad bandwidth and the first and second narrow bandwidths.