Low power differential amplifier powered by multiple unequal power supply voltages

• US 6,833,760 B1
• Filed: 07/07/2003
• Issued: 12/21/2004
• Est. Priority Date: 07/07/2003
• Status: Active Grant

• Current Assignee: Midtronics Incorporated, National Semiconductor Corporation (Texas Instruments, Inc.)
• Original Assignee: National Semiconductor Corporation (Texas Instruments, Inc.)
• Inventors: Aude, Arlo
• Primary Examiner(s): Mottola, Steven J.
• Application Number:
  US10/614,321
• Time in Patent Office: 533 Days
• Field of Search: 330/252, 330/253, 330/255, 330/261, 330/297, 330/258, 330/259
• US Class Current: 330/297
• CPC Class Codes: H03F 1/086 with FET's
• CPC Class Codes: H03F 2200/516 Some amplifier stages of an amplifier use supply voltages of different value
• CPC Class Codes: H03F 2203/45651 the LC comprising two cascode current sources
• CPC Class Codes: H03F 2203/45722 the LC comprising one or more source followers, as post buffer or driver stages, in cascade in the LC
• CPC Class Codes: H03F 3/45188 Non-folded cascode stages

Abstract

A low power differential amplifier powered by a plurality of unequal power supply voltages. The input stage operates at a higher power supply voltage so as to maintain its transistors in operational states of saturation while providing a sufficient dynamic signal voltage range. The output stage operates at a lower power supply voltage while providing a sufficient dynamic signal current range.

Claims

1. An apparatus including a low power differential amplifier powered by a plurality of unequal power supply voltages, comprising:

a first power supply terminal to convey a first power supply voltage having a first voltage magnitude;

a second power supply terminal to convey a second power supply voltage having a second voltage magnitude which is less than said first voltage magnitude;

telescopic differential amplifier circuitry, coupled to said first power supply terminal, that responds to reception of said first power supply voltage and an input differential signal by providing an intermediate differential signal corresponding to said input differential signal; and

voltage follower circuitry, coupled to said second power supply terminal and said telescopic differential amplifier circuitry, that responds to reception of said second power supply voltage and said intermediate differential signal by providing an output differential signal corresponding to said intermediate differential signal.

2. The apparatus of claim 1, wherein said telescopic differential amplifier circuitry comprises:

a first circuit branch including a first signal transistor and a first bias transistor coupled in series that responds to said first power supply voltage by conveying a portion of a predetermined current;

a second circuit branch including a second signal transistor and a second bias transistor coupled in series that responds to said first power supply voltage by conveying another portion or said predetermined current; and

current source circuitry, coupled to said first and second circuit branches, that responds to said first power supply voltage by conveying said predetermined current.

3. The apparatus of claim 1, wherein said voltage follower circuitry comprises:

a first transistor that responds to said second power supply voltage by conveying a first predetermined current;

first current source circuitry, coupled to said first transistor, that responds to said second power supply voltage by conveying said first predetermined current,

a second transistor that responds to said second power supply voltage by conveying a second predetermined current; and

second current source circuitry, coupled to said second transistor, that responds to said second power supply voltage by conveying said second predetermined current.

4. The apparatus of claim 3, wherein said first and second predetermined currents are substantially equal.

5. The apparatus of claim 1, wherein

said telescopic differential amplifier circuitry, responsive to said first power supply voltage, bas a first common mode output voltage associated therewith;

said voltage follower circuitry, responsive to said second power supply voltage, has a second common mode output voltage associated therewith; and

said first and second common mode output voltages differ by a predetermined amount.

6. The apparatus of claim 5, wherein said low power differential amplifier further comprises bias circuitry, coupled to said telescopic differential amplifier circuitry and said voltage follower circuitry, that responds to reception of said first and second common mode output voltages by providing at least one bias signal such that said predetermined amount is approximately zero.

7. The apparatus of claim 1, wherein:

said first power supply terminal is further to convey a first power supply current having a first current magnitude;

said second power supply terminal is further to convey a second power supply current having a second current magnitude, wherein said first current magnitude is less than said second current magnitude;

said telescopic differential amplifier circuitry responds to reception of said first power supply voltage, said first power supply current and said input differential signal by providing said intermediate differential signal; and

said voltage follower circuitry responds to reception of said second power supply voltage, said second power supply current and said intermediate differential signal by providing said output differential signal.

8. The apparatus of claim 7, wherein:

said telescopic differential amplifier circuitry, responsive to said first power supply voltage, has a first common mode output voltage associated therewith;

said voltage follower circuitry, responsive to said second power supply voltage, has a second common mode output voltage associated therewith; and

said first and second common mode output voltages differ by a predetermined amount.

9. An apparatus including a low power differential amplifier powered by a plurality of unequal power supply voltages, comprising:

first power means for conveying a first power supply voltage having a first voltage magnitude;

second power means for conveying a second power supply voltage having a second voltage magnitude which is less than said first voltage magnitude;

differential amplifier means for receiving said first power supply voltage and an input differential and responding thereto by generating an intermediate differential signal corresponding to said input differential signal; and

voltage follower means for receiving said second power supply voltage and said intermediate differential signal and responding thereto by generating an output differential signal corresponding to said intermediate differential signal.

10. The apparatus of claim 9, wherein

said differential amplifier means is first for receiving said first power supply voltage and responding thereto by generating a first common mode output voltage;

said voltage follower means is further for receiving said second power supply voltage and responding thereto by generating a second common mode output voltage; and

said low power differential amplifier further comprises biasing means for receiving said first and second common mode output voltages and responding thereto by generating at least one bias signal such that said first and second common mode output voltages are substantially equal.

11. An apparatus including a low power differential amplifier powered by a plurality of unequal power supply voltages, comprising:

a first power supply terminal to convey a first power supply voltage having a first voltage magnitude and a first power supply current having a first current magnitude;

a second power supply terminal to convey a second power supply voltage having a second voltage magnitude and a second power supply current having a second current magnitude, wherein said first voltage magnitude is greater than said second voltage magnitude and said first current magnitude is less than said second current magnitude;

first amplifier circuitry, coupled to said first power supply terminal, that responds to reception of said first power supply voltage, said first power supply current and an input differential signal by providing an intermediate differential signal corresponding to said input differential signal, and includes

a first circuit branch that responds to said first power supply voltage by conveying a portion of a predetermined current,

a second circuit branch that responds to said first power supply voltage by conveying another portion of said predetermined current, and

current source circuitry, coupled to said first and second circuit branches, that responds to said first power supply voltage by conveying said predetermined current; and

second amplifier circuitry, coupled to said second power supply terminal and said first amplifier circuitry, that responds to reception of said second power supply voltage, said second power supply current and said intermediate differential signal by providing an output differential signal corresponding to said intermediate differential signal.

12. An apparatus including a low power differential amplifier powered by a plurality of unequal power supply voltages, comprising:

a first power supply terminal to convey a first power supply voltage having a first voltage magnitude and a first power supply current having a first current magnitude;

a second power supply terminal to convey a second power supply voltage having a second voltage magnitude and a second power supply current having a second current magnitude, wherein said first voltage magnitude is greater than said second voltage magnitude and said first current magnitude is less than said second current magnitude;

first amplifier circuitry, coupled to said first power supply terminal, that responds to reception of said first power supply voltage, said first power supply current and an input differential signal by providing an intermediate differential signal corresponding to said input differential signal; and

second amplifier circuitry, coupled to said second power supply terminal and said first amplifier circuitry, that responds to reception of said second power supply voltage, said second power supply current ard said intermediate differential signal by providing an output differential signal corresponding to said intermediate differential signal, and includes

a first transistor that responds to said second power supply voltage by conveying a first predetermined current,

first current source circuitry, coupled to said first transistor, that responds to said second power supply voltage by conveying said first predetermined current,

a second transistor that responds to said second power supply voltage by conveying a second predetermined current, and

second current source circuitry, coupled to said second transistor, that responds to said second power supply voltage by conveying said second predetermined current.

13. The apparatus of claim 12, wherein said first and second predetermined currents are substantially equal.

14. An apparatus including a low power differential amplifier powered by a plurality of unequal power supply voltages, comprising:

a first power supply terminal to convey a first power supply voltage having first voltage magnitude and a first power supply current having a first current magnitude;

a second power supply terminal to convey a second power supply voltage having a second voltage magnitude and a second cower supply current having a second current magnitude, wherein said first voltage magnitude is greater than said second voltage magnitude and said first current magnitude is less than said second current magnitude;

first amplifier circuitry, coupled to said first power supply terminal, that responds to reception of said first power supply voltage, said first power supply current and an input differential signal by providing an intermediate differential signal corresponding to said input differential signal; and

second amplifier circuitry, coupled to said second power supply terminal and said first amplifier circuitry, that responds to reception of said second power supply voltage, said second power supply current mid said intermediate differential signal by providing an output differential signal corresponding to said intermediate differential signal;

wherein

said intermediate differential signal has an intermediate signal magnitude,

said output differential signal has an output signal magnitude, and

said intermediate and output signal magnitudes are substantially equal.

15. An apparatus including a low power differential amplifier powered by a plurality of unequal power supply voltages, comprising:

a first power supply terminal to convey a first power supply voltage having a first voltage magnitude and a first power supply current having first current magnitude;

a second power supply terminal to convey a second power supply voltage having a second voltage magnitude and a second power supply current having a second current magnitude, wherein said first voltage magnitude is greater than said second voltage magnitude and said first current magnitude is less than said second current magnitude;

first amplifier circuitry coupled to said first power supply terminal, that responds to reception of said first power supply voltage, said first power supply current and an input differential signal providing an intermediate differential signal corresponding to said input differential signal; and

second amplifier circuitry, coupled to said second power supply terminal and said first amplifier circuitry, that responds to reception of said second power supply voltage, said second power supply current and said intermediate differential signal by providing an output differential, signal corresponding to aid intermediate differential signal;

wherein

said first amplifier circuitry, responsive to said first power supply voltage, has a first common mode output voltage associated therewith,

said second amplifier circuitry, responsive to said second power supply voltage, has a second common inode output voltage associated therewith, and

said first and second common mode output voltages differ by a predetermined amount.

16. The apparatus of claim 15, wherein said low power differential amplifier further comprises bias circuitry, coupled to said first amplifier circuitry and said second amplifier circuitry, that responds to reception of said first and second common mode output voltages by providing at least one bias signal such that said predetermined amount is approximately zero.

17. An apparatus including a low power differential amplifier powered by a plurality of unequal power supply voltages, comprising:

first power means for conveying a first power supply voltage having a first voltage magnitude and a first power supply current having a first current magnitude;

second power means for conveying a second power supply voltage having a second voltage magnitude and a second power supply current having a second current magnitude, where said first voltage magnitude is greater than said second voltage magnitude and said first current magnitude is less than said second current magnitude;

first amplifier means for receiving said fist power supply voltage, said first power supply current and an input differential signal and responding thereto by generating an intermediate differential signal corresponding to said input differential signal, and further for receiving said first power supply voltage and responding thereto by generating a first common mode output voltage;

second amplifier means for receiving said second power supply voltage, said power supply current and said intermediate differential signal and responding thereto by generating an output differential signal corresponding to said intermediate differential signal, and further for receiving said second power supply voltage and responding thereto by generating a second common mode output voltage; and

biasing means for receiving said first and second common mode output voltages and responding thereto by generating at least one bias signal such that said first and second common mode output voltages are substantially equal.