High-sensitivity, low-noise transistor amplifier

• US 5,192,920 A
• Filed: 03/18/1992
• Issued: 03/09/1993
• Est. Priority Date: 03/18/1992
• Status: Expired due to Fees

• Current Assignee: Eastman Kodak Company
• Original Assignee: Eastman Kodak Company
• Inventors: Stevens, Eric G., Nelson, Edward T., Boisvert, David M.
• Primary Examiner(s): Mullins, James B.
• Application Number:
  US07/854,046
• Time in Patent Office: 356 Days
• Field of Search: 330/156, 330/277, 330/292, 330/307, 377/59, 377/60
• US Class Current: 330/277
• CPC Class Codes: H03F 1/0233 by using a signal derived from the output signal, e.g. bootstrapping the voltage supply
• CPC Class Codes: H03F 2200/372 Noise reduction and elimination in amplifier
• CPC Class Codes: H03F 3/345 with field-effect devices H03F3/347 takes precedence

Abstract

A high-gain, low-noise transistor amplifier comprises an input, an output, and first and second field effect transistors each having a gate, a drain, and a source and being formed in a common semiconductor substrate. The second transistor is a depletion mode transistor if it is of the same conductivity type as the first but is an enhancement mode transistor if it is of opposite conductivity type with respect to the first. In an amplifier configuration, the input is coupled to the gate of the first transistor, the source of the first transistor is coupled to the gate of the second transistor, the source of the second transistor is coupled to the output, and there is a direct-coupled feedback path from the source of the second transistor to the drain of the first transistor. At least the first transistor is formed in an isolated well of conductivity opposite to that of the substrate in the semiconductor substrate and its source is coupled directly to that well.

Claims

1. An amplifier comprising:

an input, an output, and first and second field effect transistors each having a gate, a drain, and a source and being formed on a common semiconductor substrate;

the second transistor being of a mode selected from a group consisting of depletion mode and enhancement mode;

the first and second transistors being of conductivity types selected from a group consisting of the same conductivity types and opposite conductivity types;

the second transistor being depletion mode with first and second transistors being of the same conductivity types;

the second transistor being enhancement mode with first and second transistors being of opposite conductivity types;

means coupling the input to the gate of the first transistor;

means coupling the source of the first transistor to the gate of the second transistor;

means coupling the source of the second transistor to the output; and

a direct-coupled feedback path from the source of the second transistor to the drain of the first transistor.

2. The amplifier of claim 1 in which the first transistor is formed in an isolated well in the substrate, the well being of opposite conductivity type with respect to the substrate, and which further comprises means coupling the source of the first transistor to its own well.

3. The amplifier of claim 1 further comprising means for coupling a voltage source between the sources and drains of both of the transistors.

4. The amplifier of claim 3 further comprising means for coupling a first substantially constant current source to the source of the first transistor and means for coupling a second substantially constant current source to the source of the second transistor.

5. The amplifier of claim 4 in which the first transistor is formed in an isolated well in the substrate, the well being of opposite conductivity type with respect to the substrate, and which further comprises means coupling the source of the first transistor to its own well.

6. An amplifier comprising:

an input, an output, and first and second field effect transistors of the same conductivity type each having a gate, a drain, and a source and being formed on a common semiconductor substrate, the second transistor being a depletion mode transistor;

means coupling the input to the gate of the first transistor;

means coupling the source of the first transistor to the gate of the second transistor;

means coupling the source of the second transistor to the output; and

a direct-coupled feedback path from the source of the second transistor to the drain of the first transistor.

7. The amplifier of claim 6 in which both of the transistors are formed in isolated wells in the substrate, the wells being of opposite conductivity type from the substrate, and which further comprises means coupling the source of each of the transistors to its own well.

8. The amplifier of claim 6 further comprising means for coupling a voltage source between the sources and drains of both of the transistors.

9. The amplifier of claim 8 further comprising means for coupling a first substantially constant current source to the source of the first transistor and means for coupling a second substantially constant current source to the source of the second transistor.

10. The amplifier of claim 9 in which both of the transistors are formed in isolated wells in the substrate, the wells being of opposite conductivity type from the substrate, and which further comprises means coupling the source of each of the transistors to its own well.

11. An amplifier comprising:

an input, an output, and first and second field effect transistors of opposite conductivity types each having a gate, a drain, and a source and being formed on a common semiconductor substrate, the second transistor being an enhancement mode transistor;

means coupling the input to the gate of the first transistor;

means coupling the source of the first transistor to the gate of the second transistor;

means coupling the source of the second transistor to the output; and

a direct-coupled feedback path from the source of the second transistor to the drain of the first transistor.

12. The amplifier of claim 11 in which the first transistor is formed in an isolated well in the substrate, the well being of opposite conductivity type from the substrate, and which further comprises means coupling the source of the first transistor to its own well.

13. The amplifier of claim 11 further comprising means for coupling a voltage source between the sources and drains of both of the transistors.

14. The amplifier of claim 13 further comprising means for coupling a first substantially constant current source to the source of the first transistor and means for coupling a second substantially constant current source to the source of the second transistor.

15. The amplifier of claim 14 in which the first transistor is formed in an isolated well in the substrate, the well being of opposite conductivity type from the substrate, and which further comprises means coupling the source of the first transistor to its own well.

16. An amplifier comprising:

a semiconductor substrate;

first and second separated field effect transistors of the same conductivity type each of which is formed in the substrate and having a drain, a source, and a gate, the second transistor being a depletion mode transistor;

first and second constant current sources formed in the substrate;

the source of the first transistor being coupled to the first constant current source and the gate of the second transistor;

the gate of the first transistor being adapted to serve as an input of the amplifier;

the source of the second transistor being coupled to the second constant current source and to an output of the amplifier; and

a direct-coupled feedback path between the source of the second transistor and the drain of the first transistor.

17. An amplifier comprising:

a semiconductor substrate;

first and second separated field effect transistors of opposite conductivity types each of which is formed in the substrate and having a drain, a source, and a gate, the second transistor being an enhancement mode transistor;

first and second constant current sources formed in the substrate;

the source of the first transistor being coupled to the first constant current source and the gate of the second transistor;

the gate of the first transistor being adapted to serve as an input of the amplifier;

the source of the second transistor being coupled to the second constant current source and to an output of the amplifier; and

a direct-coupled feedback path between the source of the second transistor and the drain of the first transistor.