Modified distributed amplifier to improve low frequency efficiency and noise figure
A distributed amplifier system has a predetermined output impedance and input impedance and includes an input transmission circuit; an output transmission circuit; at least two amplifiers connected between the input and output transmission circuits; an input termination on the input transmission circuit; and a feedback output termination on the output transmission circuit connected back to the input transmission circuit for reducing low frequency loss while maintaining the predetermined output impedance and input impedance.
1. A distributed amplifier system having a predetermined output impedance and input impedance comprising:
an input transmission circuit;
an output transmission circuit;
at least two amplifiers connected between said input and output transmission circuits;
an input termination on the input transmission circuit; and
a feedback output termination including a high pass filter coupled between the output transmission circuit and the input transmission circuit for reducing low frequency loss while maintaining said predetermined output impedance and input impedance.
2. The distributed amplifier system of claim 1 in which said plurality of amplifiers includes two amplifiers.
3. The distributed amplifier system of claim 1 in which said amplifiers include cascode amplifiers.
4. The distributed amplifier system of claim 1 in which said input termination includes an input resistance and an input capacitance connected in series to ground.
5. The distributed amplifier system of claim 1 in which the high pass filter of said output termination includes an output resistance and an output capacitance connected in series.
6. The distributed amplifier system of claim 5 in which said output resistance is substantially larger than said predetermined output impedance.
7. The distributed amplifier system of claim 6 in which output resistance is at least twice said predetermined output impedance.
8. The distributed amplifier system of claim 7 in which said output resistance is in the range of two to twenty times said predetermined output impedance.
9. The distributed amplifier system of claim 4 in which said input resistance is substantially larger than said predetermined input impedance for reducing the overall noise figure of said amplifier system.
10. The distributed amplifier system of claim 1 in which said feedback output termination is fed back to the input of said input transmission circuit.
11. The distributed amplifier system of claim 1 in which there is more than one feedback output termination connection between said output transmission circuit and said input transmission circuit.
12. The distributed amplifier system of claim 1 in which the feedback output termination coupled between the output transmission circuit and the input transmission circuit includes only passive components.
13. A distributed amplifier system having a predetermined output impedance and input impedance comprising:
an input transmission circuit;
an output transmission circuit;
at least two amplifiers connected between said input and output transmission circuits;
an input termination on the input transmission circuit; and
two or more feedback output terminations on the output transmission circuit connected back to the input transmission circuit for reducing low frequency loss while maintaining said predetermined output impedance and input impedance.
14. The distributed amplifier system of claim 13 in which each output termination includes an output resistance and an output capacitance connected in series.
15. The distributed amplifier system of claim 13 in which the feedback output termination coupled between the output transmission circuit and the input transmission circuit includes only passive components.