Apparatus for input amplifier stage
First Claim
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1. An amplifier having an output, comprising in combination:
- a high gain, low noise differential input stage including inverting input transistor means and non-inverting second transistor means, the base of the second transistor means to be controlled by a predetermined voltage wherein the emitter cross-sectional area of the second transistor is significantly greater than the emitter cross-sectional area of the input transistor;
means for biasing the input transistor means and the second transistor means to substantially equal base to emitter voltages, thereby dividing the quiescent emitter current between the input transistor means and the second transistor means in substantially the same ratio as the emitter cross-sectional areas; and
means for providing feedback from the output to the base of the input transistor means.
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Abstract
A differential stage of an amplifier includes an input transistor and a second transistor with a significantly greater emitter cross-sectional area than the input transistor. Quiescent emitter current is divided between the two transistors in substantially the same ratio as the emitter cross-sectional areas so that the emitter current densities are substantially equal.
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Citations
15 Claims
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1. An amplifier having an output, comprising in combination:
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a high gain, low noise differential input stage including inverting input transistor means and non-inverting second transistor means, the base of the second transistor means to be controlled by a predetermined voltage wherein the emitter cross-sectional area of the second transistor is significantly greater than the emitter cross-sectional area of the input transistor; means for biasing the input transistor means and the second transistor means to substantially equal base to emitter voltages, thereby dividing the quiescent emitter current between the input transistor means and the second transistor means in substantially the same ratio as the emitter cross-sectional areas; and means for providing feedback from the output to the base of the input transistor means. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. An amplifier having an output, comprising in combination:
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a high gain, low noise differential input stage including inverting input transistor means and non-inverting second transistor means to be controlled by a predetermined voltage; means for biasing the input transistor means and the second transistor means wherein the quiescent current is substantially different in the second transistor means from the quiescent current in the input transistor means; and means for providing feedback from the output to the base of the input transistor means. - View Dependent Claims (10, 11, 12)
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13. An amplifier having an output, to be used with means for generating a reference voltage, comprising in combination:
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a high gain, low noise differential input stage including inverting input transistor means and non-inverting second transistor means to be controlled by a predetermined voltage; means for biasing the input transistor means and the second transistor means wherein the quiescent current is substantially different in the second transistor means from the quiescent current in the input transistor means; a capacitor, wherein the voltage across the capacitor is responsive to the voltage output of the amplifier averaged over a period of time; a first current divider branch connected to the base of the input transistor means and having a predetermined quiescent current; resistance means connecting the reference voltage to the common connection of the first current branch and the input transistor means for providing current to the first current divider branch; and a second current divider branch connected to the first current divider branch at the end opposite the resistance means and the input transistor means, wherein the current in the second current divider branch is controlled by the voltage across the capacitor, the quiescent current in the second branch being significantly greater than the quiescent current in first branch, whereby the combination of the capacitor, the first current divider branch and the second current divider branch act as an automatic gain control circuit connected in a feedback relationship to the amplifier. - View Dependent Claims (14, 15)
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Specification