Linear amplifier
First Claim
1. An integrated circuit amplifier comprising:
- a differential pair of input field-effect transistors (FETs) receiving a differential input voltage signal having a first input signal component and a second input signal component and providing in response thereto a differential output voltage signal having a first output signal component and a second output signal component, the differential pair of input FETs including;
a first input FET having a source terminal, a gate terminal receiving the first input signal component, and a drain terminal providing the first output signal component, anda second input FET having a source terminal coupled to the source terminal of the first input FET, a gate terminal receiving the second input signal component, and a drain terminal providing the second output signal component;
a first load FET having a source terminal, a gate terminal, a drain terminal coupled to the drain terminal of the first input FET, and a controlled conductance between the drain terminal and the source terminal;
a second load FET having a source terminal coupled to the source terminal of the first load FET, a gate terminal coupled to the gate terminal of the first load FET, a drain terminal coupled to the drain terminal of the second input FET, and a controlled conductance between the drain terminal and the source terminal; and
a dynamic bias circuit coupled to the gate terminals of the first and second load FET for keeping the first load FET and the second load FET in a nonsaturation region and for controlling the conductance between the drain terminal and the source terminal of each of the first and second load FETs by applying a varying bias voltage to the gate terminals of each of the first and second load FETs.
1 Assignment
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Accused Products
Abstract
A low-noise, low-power complementary metal-oxide-semiconductor (CMOS) integrated circuit common source differential amplifier is disclosed which is capable of amplifying low amplitude cardiac signals such as those produced by atrial depolarization of the heart. The amplifier has a pair of large area p-channel input field-effect transistors (FETs) biased in weak inversion. The amplifier also has active load FETs biased in the nonsaturation (linear) region by means of a varying gate terminal voltage applied by a dynamic bias circuit. The gate terminal voltage is varied to match the temperature dependence of the output conductance of the load FETs to the temperature dependence of the transconductance of the input FETs. The gate terminal voltage also sets a dc bias point which uses the nonlinearity in the load FET output conductance to cancel nonlinearity in the input FET transconductance.
35 Citations
24 Claims
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1. An integrated circuit amplifier comprising:
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a differential pair of input field-effect transistors (FETs) receiving a differential input voltage signal having a first input signal component and a second input signal component and providing in response thereto a differential output voltage signal having a first output signal component and a second output signal component, the differential pair of input FETs including; a first input FET having a source terminal, a gate terminal receiving the first input signal component, and a drain terminal providing the first output signal component, and a second input FET having a source terminal coupled to the source terminal of the first input FET, a gate terminal receiving the second input signal component, and a drain terminal providing the second output signal component; a first load FET having a source terminal, a gate terminal, a drain terminal coupled to the drain terminal of the first input FET, and a controlled conductance between the drain terminal and the source terminal; a second load FET having a source terminal coupled to the source terminal of the first load FET, a gate terminal coupled to the gate terminal of the first load FET, a drain terminal coupled to the drain terminal of the second input FET, and a controlled conductance between the drain terminal and the source terminal; and a dynamic bias circuit coupled to the gate terminals of the first and second load FET for keeping the first load FET and the second load FET in a nonsaturation region and for controlling the conductance between the drain terminal and the source terminal of each of the first and second load FETs by applying a varying bias voltage to the gate terminals of each of the first and second load FETs. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15)
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16. A method of signal amplification using a differential amplifier including first and second differential input FETs coupled at common source terminals, each of the first and second differential input FETs having a gate terminal, the differential amplifier further including first and second load field-effect transistors (FETs) coupled at common gate terminals and common source terminals, the first and second load FETs each having a drain terminal coupled to a corresponding drain terminal of first and second input FETs respectively, the method comprising the steps of:
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receiving a differential input voltage signal between the gate terminals of each of the first and second input FETs; amplifying the differential input voltage signal by a linear amplification voltage gain resulting in a differential output voltage signal, the linear amplification voltage gain varying with temperature according to a temperature sensitivity; and biasing the common gate terminals of the first and second load FETs with a varying bias voltage to reduce the temperature sensitivity of the linear amplification voltage gain. - View Dependent Claims (17, 18, 19, 20, 21)
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22. A cardiac rhythm management system, comprising:
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at least one sensing electrode for sensing electrical depolarization signals produced by a heart; an amplifier having first and second input ports coupled to the sensing electrode and receiving the sensed electrical depolarization signals as a differential input voltage signal between the first and second input ports, the differential input voltage signal having a first input signal component at the first input port and a second input signal component at the second input port, and the amplifier providing in response thereto a differential output voltage signal having a first output signal component and a second output signal component, the amplifier comprising; a first input field-effect transistor (FET) having a source terminal, a gate terminal coupled to the first input port and receiving the first input signal component, and a drain terminal providing the first output signal component; a second input FET having a source terminal coupled to the source terminal of the first input FET, a gate terminal receiving the second input signal component, and a drain terminal providing the second output signal component; a first load FET having a source terminal, a gate terminal, a drain terminal coupled to the drain terminal of the first input FET, and a controlled conductance between the drain terminal and the source terminal; a second load FET having a source terminal coupled to the source terminal of the first load FET, a gate terminal coupled to the gate terminal of the first load FET, a drain terminal coupled to the drain terminal of the second input FET, and a controlled conductance between the drain terminal and the source terminal; and a dynamic bias circuit coupled to the gate terminals of the first and second load FETs for keeping the first load FET and the second load FET in a nonsaturation region and for controlling the conductance between the drain terminal and the source terminal of each of the first and second load FETs by applying a varying bias voltage to the gate terminals of each of the first and second load FETs. - View Dependent Claims (23, 24)
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Specification