Variable-gain circuit
First Claim
1. A variable-gain circuit comprising a functional circuit for receiving an input signal to output an output signal having a gain with respect said input signal, a first gain control section for receiving a first control signal to control said functional circuit to operate based on a first gain curve of decibel gain plotted in a graph against said first control signal, said first gain curve being convex toward a bottom of the graph, a second gain control section for receiving a second control signal to control said functional circuit to operate based on a second gain curve of decibel gain plotted in a graph against said second control voltage, said second gain curve being convex toward a top of the graph, said first and second control signals being applied so that said first gain curve and said second gain curve cancel each other in non-linearity.
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Accused Products
Abstract
A variable-gain circuit includes an amplifying transistor, a first gain control section for receiving a first gain control signal to control the amplifying transistor to have a first gain curve of decibel gain convex toward the bottom of graph, and a second gain control section for receiving a second control signal to control the first transistor to have a second gain curve of decibel gain convex toward the top of graph. The first and second control signals are fed at a time to cancel the non-linearity of the gain curves to have an overall linear gain curve.
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Citations
12 Claims
- 1. A variable-gain circuit comprising a functional circuit for receiving an input signal to output an output signal having a gain with respect said input signal, a first gain control section for receiving a first control signal to control said functional circuit to operate based on a first gain curve of decibel gain plotted in a graph against said first control signal, said first gain curve being convex toward a bottom of the graph, a second gain control section for receiving a second control signal to control said functional circuit to operate based on a second gain curve of decibel gain plotted in a graph against said second control voltage, said second gain curve being convex toward a top of the graph, said first and second control signals being applied so that said first gain curve and said second gain curve cancel each other in non-linearity.
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12. A variable-gain circuit comprising a first transistor having an emitter connection and a base connected to an input terminal via a capacitor for receiving an input signal to output an output signal having a gain with respect to said input signal, a base bias circuit including first through third resistors, said base of said first transistor being connected to a first node connecting said first and second resistors together, a second transistor having a base for receiving a gain control signal, an emitter connected to a node connecting said first and second resistors together, and a collector connected to said input terminal and to a reference potential line via a fourth resistor.
Specification