Digitally controlled gain stage having an analogue control input
First Claim
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1. Gain control circuitry for controlling the gain of a signal path, the gain control circuitry comprising:
- comparator circuitry configured to receive a first analogue input and provide a first digital output in response to receiving the first analogue input having a value greater than an upper threshold value or less than a lower threshold value;
a bi-directional counter configured to provide a digital gain control signal to a digitally controlled gain device and configured to change the value of the digital gain control signal in response to receiving the first digital output from the comparator circuitry;
a digital-to-analogue converter configured to convert the digital gain control signal to a first analogue output signal;
a subtractor configured to receive the first analogue output signal from the digital-to-analogue converter and an analogue gain control signal and to provide a second analogue output signal representative of the difference between the value of the first analogue output signal from the digital-to-analogue converter and the analogue gain control signal, the second analogue output signal being provided as the first analogue input to the comparator circuitry.
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Abstract
A signal processing system has a first, digitally controlled, gain element, a second, analogue controlled, gain element and a gain control unit configured to receive a gain request signal and to generate a first gain control signal to be input to the first gain element and a second gain control signal to be input to the second gain element such that the gain provided by the signal processing system corresponds to the gain request signal.
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Citations
13 Claims
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1. Gain control circuitry for controlling the gain of a signal path, the gain control circuitry comprising:
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comparator circuitry configured to receive a first analogue input and provide a first digital output in response to receiving the first analogue input having a value greater than an upper threshold value or less than a lower threshold value; a bi-directional counter configured to provide a digital gain control signal to a digitally controlled gain device and configured to change the value of the digital gain control signal in response to receiving the first digital output from the comparator circuitry; a digital-to-analogue converter configured to convert the digital gain control signal to a first analogue output signal; a subtractor configured to receive the first analogue output signal from the digital-to-analogue converter and an analogue gain control signal and to provide a second analogue output signal representative of the difference between the value of the first analogue output signal from the digital-to-analogue converter and the analogue gain control signal, the second analogue output signal being provided as the first analogue input to the comparator circuitry. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. A gain control system for controlling the gain applied to a signal, the gain control system comprising:
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a digitally controlled gain element configured to receive a first input signal and a first digital gain control signal, and to apply a gain to the first input signal in accordance with the digital gain control signal; an analogue controlled gain element configured to receive a second input signal and a first analogue gain control signal and to apply a gain to the second input signal in accordance with the received first analogue gain control signal; comparator circuitry configured to receive a first analogue input and provide a digital output in response to the first analogue input having a value greater than an upper threshold value or less than a lower threshold value; a bi-directional counter configured to provide the first digital gain control signal and to change the value of the first digital gain control signal in response to receiving the digital output from the comparator circuitry; a digital-to-analogue converter configured to convert the first digital gain control signal to an analogue signal; and a subtracting element configured to receive the analogue signal from the digital-to-analogue converter and a second analogue gain control signal and to provide an analogue output signal representative of the difference in value between the second analogue gain control signal and the digital gain control signal, the analogue output signal being provided as the analogue input signal to the comparator circuitry and as the first analogue control signal to the analogue controlled gain element.
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Specification