Low noise cascode amplifier
The present invention relates to a low noise cascode amplifier comprising a first transistor, a second transistor, a third transistor, a first inductor, and a second inductor. Furthermore, the first transistor can connect with the second transistor via the first inductor, and the second transistor can connect with the third transistor via the second inductor; thereby, a cascode device can be formed. The inductor and the parasitic capacitances can resonate at high frequency, so that the noise figure of the cascode amplifier can be reduced.
1. A low noise cascode amplifier, comprising:
a first transistor;
a first inductor connected to said first transistor, a first parasitic capacitance being generated between said first transistor and said first inductor;
a second transistor connected to said first inductor, a second parasitic capacitance being generated between said first inductor and said second transistor;
a second inductor connected to said second transistor, a third parasitic capacitance being generated between said second transistor and said second inductor; and
a third transistor connected to said second inductor, a fourth parasitic capacitance being generated between said second inductor and said third transistor.
2. The low noise cascode amplifier of claim 1 , wherein the inductance of said first inductor and said second inductor is adjusted according to the value of said first parasitic capacitance, said second parasitic capacitance, said third parasitic capacitance, and said fourth parasitic capacitance.
3. The low noise cascode amplifier of claim 2 , wherein the inductance of said first inductor and said second inductor is adjusted according to the operating frequency of said amplifier.
4. The low noise cascode amplifier of claim 1 , wherein the value of said first parasitic capacitance is Cp 1 , the value of said second parasitic capacitance is Cp 2 , the operating frequency of said amplifier is ω, and the inductance L 1 of said first inductor is approximately (C p1 +C p2 )/ω 2 C p1 C p2 .
5. The low noise cascode amplifier of claim 1 , wherein the value of said third parasitic capacitance is Cp 3 , the value of said fourth parasitic capacitance is Cp 4 , the operating frequency of said amplifier is ω, and the inductance L 2 of said second inductor is approximately (C p3 +C p4 )/ω 2 C p3 C p4 .
6. A low noise cascode amplifier comprising:
a first transistor;
a first inductor connected to said first transistor;
a second transistor connected to said first inductor;
a second inductor connected to said second transistor;
a third transistor connected to said second inductor; and
at least one nth transistor and at least one (n−1)th inductor, wherein n is an integer equal to or greater than 4, said nth transistor being connected to said third transistor via said (n−1)th inductor.
7. The low noise cascode amplifier of claim 1 , wherein the gate of said first transistor connects to a first resistance, the gate of said second transistor connects to a second resistance, and the gate of said third transistor connects to a third resistance.
8. The low noise cascode amplifier of claim 1 , further comprising an input terminal that connects to a first T-matching network and an output terminal that connects to a second T-matching network.
9. A low noise cascode amplifier, comprising:
a cascode device comprising three or more transistors in series, each of said transistors having a gate connected to a resistance; and
at least one inductor positioned between said adjacent transistors, a respective parasitic capacitance being generated between each of said transistors and a corresponding inductor.
10. A low noise cascode amplifier, comprising:
a cascode device comprising three or more transistors in series;
at least one inductor positioned between said adjacent transistors, a respective parasitic capacitance being generated between each of said transistors and a corresponding inductor; and
an input terminal that connects to a first T-matching network, and an output terminal that connects to a second T-matching network.
11. A low noise cascode amplifier, comprising:
a cascode device comprising three or more transistors in series, said cascode device comprises a first transistor, a second transistor, a third transistor, and an nth transistor, wherein n is an integer equal to or greater than 4; and
at least one inductor positioned between said adjacent transistors, a respective parasitic capacitance being generated between each of said transistors and a corresponding inductor.