Logarithmic amplifier gain stage
First Claim
1. A logarithmic amplifier gain stage for supplying, in response to an instantaneous input signal, an output signal representing a portion of a corresponding logarithmic value of the input signal, comprising:
- a transistor amplifier having an input that receives the input signal and an intermediate output that supplies an intermediate output signal; and
a full-wave detector having an input coupled to the intermediate output of the transistor amplifier that receives the intermediate output signal and an output that supplies the output signal, the detector including a rectifier comprising rectifying transistors having different effective emitter areas for demodulating a signal applied to the input of the full-wave detector, wherein each rectifying transistor has a base and all bases of the rectifying transistors are coupled together by a single bias line.
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Abstract
A logarithmic amplifier gain stage for supplying, in response to an instantaneous input signal, an output signal representing a portion of a corresponding logarithmic value of the input signal. The gain stage includes a transistor amplifier having an input that receives the input signal and an intermediate output that supplies an intermediate output signal. A full-wave detector having an input coupled to the intermediate output of the transistor amplifier receives the intermediate output signal and supplies the output signal wherein the detector includes a rectifier comprising transistors having different effective emitter areas. The different emitter areas can be formed by physical differences in emitter area of the full-wave rectifier transistors. In another embodiment of the invention, the different emitter areas can be synthesized by controlling a voltage between a base and an emitter of at least one transistor in the full-wave rectifier. The full-wave detector performs the demodulating function and also drives the input of a succeeding gain stage.
60 Citations
22 Claims
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1. A logarithmic amplifier gain stage for supplying, in response to an instantaneous input signal, an output signal representing a portion of a corresponding logarithmic value of the input signal, comprising:
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a transistor amplifier having an input that receives the input signal and an intermediate output that supplies an intermediate output signal; and a full-wave detector having an input coupled to the intermediate output of the transistor amplifier that receives the intermediate output signal and an output that supplies the output signal, the detector including a rectifier comprising rectifying transistors having different effective emitter areas for demodulating a signal applied to the input of the full-wave detector, wherein each rectifying transistor has a base and all bases of the rectifying transistors are coupled together by a single bias line. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. A logarithmic amplifier gain stage for supplying, in response to an instantaneous input signal, an output signal representing a portion of a corresponding logarithmic value of the input signal, comprising:
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a transistor amplifier having an input that receives the input signal and an intermediate output that supplies an intermediate output signal; and a full-wave detector having an input coupled to the intermediate output of the transistor amplifier that receives the intermediate output signal and an output that supplies the output signal, the detector including at least two half-wave rectifies, each half-wave rectifier comprising a pair of transistors having different effective emitter areas and a resistor coupling a base of each transistor in the pair together and wherein a base of one of the transistors in one of the at least two half-wave rectifiers is coupled to a base of one of the transistors in another of the at least two half-wave rectifiers. - View Dependent Claims (13, 14, 15, 16, 17, 18, 19, 20, 21, 22)
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Specification