Low distortion amplifier
AssigneeTelASIC Communications, Inc.
InventorsDon C. Devendorf, Lloyd F. Linder, Cuong D. Tran
Life of this patent
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Abstract
A low distortion amplifier. The novel amplifier includes a first transistor Q1 having first and second output terminals and an input terminal adapted to receive an input signal, and a second transistor Q2 having first and second output terminals and an input terminal adapted to receive a signal from the first output terminal of Q1, wherein the second output terminal of Q1 is connected to the second output terminal of Q2 in order to eliminate a nonlinear current component in Q2. In an illustrative embodiment, the amplifier also includes a cascode Darlington pair Q3, Q4 for holding the second output terminals of Q1 and Q2 at a desired voltage to further reduce distortion and to maintain a wide bandwidth.
Claims32
An amplifier comprising:
- a first transistor Q1 having first and second output terminals and an input terminal adapted to receive an input signal;
- a constant current source coupled to said first output terminal of Q1;
- and
- a second transistor Q2 having first and second output terminals and an input terminal adapted to receive a signal from said first output terminal of Q1, wherein said second output terminal of Q1 is connected to said second output terminal of Q2.
An amplifier comprising:
- a first transistor Q1 having first and second output terminals and an input terminal adapted to receive an input signal;
- a second transistor Q2 having first and second output terminals and an input terminal adapted to receive a signal from said first output terminal of Q1, wherein said second output terminal of Q1 is connected to said second output terminal of Q2;
- and
- a circuit for holding said second output terminals of Q1 and Q2 at a desired voltage,
- wherein said amplifier further includes a constant current source coupled to said first output terminal of Q1.
An amplifier comprising:
- a first transistor Q1 having first and second output terminals and an input terminal adapted to receive an input signal;
- a second transistor Q1 having first and second output terminals and an input terminal adapted to receive a signal from said first output terminal of Q1, wherein said second output terminal of Q1 is connected to said second Output terminal of Q2;
- and
- a circuit for holding said second output terminals of Q1 and Q2 at a desired voltage,
- wherein said circuit includes a Darlington pair comprised of a transistor Q3 having an input terminal and first and second output terminals, and a transistor Q4 having an input terminal and first and second output terminals,
- wherein said first output terminal of Q3 is connected to the input terminal of Q4,
- wherein said second output terminal of Q3 is connected to the second output terminal of Q4,
- wherein said first output terminal of Q4 is connected to the second output terminal of Q2, and
- wherein said input terminal of Q3 is connected to a reference voltage VREF.
An amplifier comprising:
- an input terminal adapted to receive an input signal;
- a first Darlington pair comprised of two transistors Q1 and Q2, wherein a first output of Q1 is connected to an input of Q2 and a second output of Q1 is connected to a second output of Q2;
- a cascode Darlington pair comprised of two transistors Q3 and Q4, wherein a first output of Q3 is connected to an input of Q4, a second output of Q3 is connected to a second output of Q4, and a first output of Q4 is connected to said second output of Q2;
- an operational amplifier having a positive input connected to said input terminal, a negative input connected to a first output of Q2, and an output connected to an input of Q1;
- an output terminal connected to said second output of Q4;
- and a capacitor C and resistor R3 connected in series between said input terminal and said output terminal.
A method for reducing distortion in an amplifier including the steps of:
- connecting two transistors Q1 and Q2 in a Darlington pair configuration wherein an input of Q1 is adapted to receive an input signal, and a first output of Q1 is connected to an input of Q2;
- coupling a constant current source to said first output of Q1;
- and
- connecting a second output of Q1 to a second output of Q2 to eliminate a nonlinear current component in Q2.
Dependencies are inferred from the claim text.