Cascode distributed amplifier

• US 6,864,750 B2
• Filed: 03/14/2002
• Issued: 03/08/2005
• Est. Priority Date: 07/11/2001
• Status: Active Grant

• Current Assignee: Fujitsu Limited
• Original Assignee: Fujitsu Limited
• Inventors: Shigematsu, Hisao
• Primary Examiner(s): Choe, Henry
• Application Number:
  US10/096,865
• Publication Number:
  US 20030011436A1
• Time in Patent Office: 1,090 Days
• Field of Search: 330/286, 330/295, 330/302, 330/311, 330/124.R, 330/310
• US Class Current: 330/311
• CPC Class Codes: H03F 1/223 with MOSFET's
• CPC Class Codes: H03F 3/607 using FET's

Abstract

In a cascode distributed amplifier of the present invention, a plurality of unit circuits are connected in parallel, and each unit circuit includes a pair of first and second transistors connected in series between an input transmission wire and an output transmission wire. The first transistor has a gate connected to the input transmission wire, a source grounded and a drain connected to the second transistor. The second transistor has a gate grounded, a source connected to the drain of the first transistor and a drain connected to the output transmission wire. Each unit circuit includes a damping resistor having a first end connected to the gate of the second transistor and a second end, and a capacitor having a first end connected to the second end of the damping resistor and a second end grounded.

Claims

1. A single-phase cascode distributed amplifier including a plurality of unit circuits connected in parallel, each unit circuit comprising:

a pair of first and second field-effect transistors connected in series between an input transmission wire and an output transmission wire, the first field-effect transistor having a gate connected to the input transmission wire, a source grounded and a drain connected to the second field-effect transistor, and the second field-effect transistor having a gate grounded, a source connected to the drain of the first field-effect transistor and a drain connected to the output transmission wire;

a damping resistor having a first end connected to the gate of the second field-effect transistor and a second end, the damping resistor prevents a rapid increase of a negative-polarity resistance of the second field-effect transistor in a high frequency range where oscillation of the amplifier tends to occur; and

a capacitor having a first end connected to the second end of the damping resistor and a second end grounded.

5. The cascode distributed amplifier of claim 1, wherein the cascode distributed amplifier receives an input signal from an input terminal at one end of the input transmission wire and supplies an amplified signal to an output terminal at one end of the output transmission wire.

13. The cascode distributed amplifier of claim 1, wherein the high frequency range in which the amplifier operates is above 40 GHz.

2. A single-phase cascode distributed amplifier including a plurality of unit circuits connected in parallel, each unit circuit comprising:

a pair of first and second field-effect transistors connected in series between an input transmission wire and an output transmission wire, the first field-effect transistor having a gate connected to the input transmission wire, a source grounded and a drain connected to the second field-effect transistor, and the second field-effect transistor having a gate grounded, a source connected to the drain of the first field-effect transistor and a drain connected to the output transmission wire;

a variable capacitor having a first end and a second end grounded, the capacitor having a variable capacitance provided to compensate for variations of frequency characteristics of a subsequently connected circuit; and

a damping resistor having a first end connected to the gate of the second field-effect transistor and a second end connected to the first end of the variable capacitor, the damping resistor prevents a rapid increase of a negative-polarity resistance of the second field-effect transistor in a high frequency range where oscillation of the amplifier tends to occur.

14. The cascode distributed amplifier of claim 2 wherein said variable capacitor is constructed by using a varactor diode.

3. A dual-phase cascode distributed amplifier including a first single-phase cascode distributed amplifier and a second single-phase cascode distributed amplifier that are connected together, each single-phase cascode distributed amplifier including a plurality of unit circuits connected in parallel, each unit circuit comprising:

a pair of first and second field-effect transistors connected in series between an input transmission wire and an output transmission wire, the first field-effect transistor having a gate connected to the input transmission wire, a source grounded and a drain connected to the second field-effect transistor, and the second field-effect transistor having a gate grounded, a source connected to the drain of the first field-effect transistor and a drain connected to the output transmission wire;

a damping resistor having a first end connected to the gate of the second field-effect transistor and a second end, the damping resistor prevents a rapid increase of a negative-polarity resistance of the second field-effect transistor in a high frequency range where oscillation of the amplifier tends to occur; and

a capacitor having a first end connected to the second end of the damping resistor and a second end grounded.

4. A dual-phase cascode distributed amplifier including a first single-phase cascode distributed amplifier and a second single-phase cascode distributed amplifier that are connected together, each single-phase cascode distributed amplifier including a plurality of unit circuits connected in parallel, each unit circuit comprising:

a pair of first and second field-effect transistors connected in series between an input transmission wire and an output transmission wire, the first field-effect transistor having a gate connected to the input transmission wire, a source grounded and a drain connected to the second field-effect transistor, and the second field-effect transistor having a gate grounded, a source connected to the drain of the first field-effect transistor and a drain connected to the output transmission wire;

a variable capacitor having a first end and a second end grounded, the capacitor having a variable capacitance provided to compensate for variations of frequency characteristics of a subsequently connected circuit; and

a damping resistor having a first end connected to the gate of the second field-effect transistor and a second end connected to the first end of the variable capacitor, the damping resistor prevents a rapid increase of a negative-polarity resistance of the second field-effect transistor in a high frequency range where oscillation of the amplifier tends to occur.

15. The cascode distributed amplifier of claim 4, wherein said variable capacitor is constructed by using a varactor diode.

6. A transmission system including a transmitter and a receiver that are connected via a transmission path, at least one of the transmitter and the receiver including a cascode distributed amplifier, the cascode distributed amplifier including a plurality of unit circuits connected in parallel, each unit circuit comprising:

a pair of first and second field-effect transistors connected in series between an input transmission wire and an output transmission wire, the first field-effect transistor having a gate connected to the input transmission wire, a source grounded and a drain connected to the second field-effect transistor, and the second field-effect transistor having a gate grounded, a source connected to the drain of the first field-effect transistor and a drain connected to the output transmission wire;

a damping resistor having a first end connected to the gate of the second field-effect transistor and a second end, the damping resistor prevents a rapid increase of a negative-polarity resistance of the second field-effect transistor in a high frequency range where oscillation of the amplifier tends to occur; and

a capacitor having a first end connected to the second end of the damping resistor and a second end grounded.

7. A single-phase cascode distributed amplifier including a plurality of unit circuits connected in parallel, each unit circuit comprising:

a pair of first and second field-effect transistors connected in series between an input transmission wire and an output transmission wire, the first field-effect transistor having a gate connected to the input transmission wire, a source grounded and a drain connected to the second field-effect transistor, and the second field-effect transistor having a gate grounded, a source connected to the drain of the first field-effect transistor and a drain connected to the output transmission wire; and

a capacitor having a first end connected to the gate of the second field-effect transistor and a second end grounded,

wherein each of at least two unit circuits among the plurality of unit circuits further includes a damping resistor provided between the second field-effect transistor and the capacitor, the damping resistor having a first end connected to the gate of the second field-effect transistor and a second end connected to the first end of the capacitor, the damping resistor prevents a rapid increase of a negative-polarity resistance of the second field-effect transistor in a high frequency range where oscillation of the amplifier tends to occur.

9. The cascode distributed amplifier of claim 7, wherein said at least two unit circuits, each including the damping resistor, are located adjacent to an input terminal of the cascode distributed amplifier.

10. The cascode distributed amplifier of claim 7, wherein said at least two unit circuits, each including the damping resistor, are located adjacent to an output terminal of the cascode distributed amplifier.

8. A dual-phase cascode distributed amplifier including a first single-phase cascode distributed amplifier and a second single-phase cascode distributed amplifier that are connected together, each single-phase cascode distributed amplifier including a plurality of unit circuits connected in parallel, each unit circuit comprising:

a pair of first and second field-effect transistors connected in series between an input transmission wire and an output transmission wire, the first field-effect transistor having a gate connected to the input transmission wire, a source grounded and a drain connected to the second field-effect transistor, and the second field-effect transistor having a gate grounded, a source connected to the drain of the first field-effect transistor and a drain connected to the output transmission wire; and

a capacitor having a first end connected to the gate of the second field-effect transistor and a second end grounded,

wherein each of at least two unit circuits among the plurality of unit circuits further includes a damping resistor provided between the second field-effect transistor and the capacitor, the damping resistor having a first end connected to the gate of the second field-effect transistor and a second end connected to the first end of the capacitor, the damping resistor prevents a rapid increase of a negative-polarity resistance of the second field-effect transistor in a high frequency range where oscillation of the amplifier tends to occur.

11. The cascode distributed amplifier of claim 8, wherein said at least two unit circuits, each including the damping resistor, are located adjacent to an input terminal of the cascode distributed amplifier.

12. The cascode distributed amplifier of claim 8, wherein said at least two unit circuits, each including the damping resistor, are located adjacent to an output terminal of the cascode distributed amplifier.