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US 6,333,675 B1Granted
Variable gain amplifier with gain control voltage branch circuit
AssigneeFujitsu Limited
InventorShinji Saito
Life of this patent
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Abstract
A variable gain amplifier includes multiple unit variable gain amplifiers connected in series which amplify an input signal in accordance with their respective gains and generate a multi-stage amplified signal. A gain control circuit generates voltage control signals, one for each of the unit amplifiers, from a gain control input signal. The control signals control the respective gains of the unit amplifiers such that the gain of the first amplifier in the series is greater than the gain of the last amplifier in the series.
Claims8
A variable gain amplifier, comprising:
- a plurality of series connected unit variable gain amplifiers including a front stage amplifier and a back stage amplifier, for amplifying an input signal in accordance with respective gains and generating a multi-stage amplified signal;
- and
- a gain control circuit, connected to the plurality of unit variable gain amplifiers, for generating control signals which control the respective gains of the unit variable gain amplifiers in accordance with a gain control input signal so that the gain of the front stage amplifier is greater than that of the back stage amplifier, wherein the gain control circuit includes,
- a control voltage branch circuit for causing the voltage of the gain control input signal to branch at a plurality of branch voltage corresponding to the unit variable gain amplifiers, each of the branch voltage having a gradient, and
- a plurality of voltage gradient regulating circuits, connected to the control voltage branch circuit, for regulating the gradients of the plurality of branch voltages to generate the control signals.
2 more elements
A variable gain amplifier, comprising:
- a plurality of series connected unit variable gain amplifiers including a front stage amplifier and a back stage amplifier, for amplifying an input signal in accordance with respective gains and generating a multi-stage amplified signal;
- and
- a gain control circuit, connected to the plurality of unit variable gain amplifiers, for generating control signals which control the respective gains of the unit variable gain amplifiers in accordance with a gain control input signal so that the gain of the front stage amplifier is greater than that of the back stage amplifier, wherein the plurality of unit variable gain amplifiers include three unit variable gain amplifiers and the gain control circuit includes:
- a first control voltage branch circuit for causing the voltage of the gain control input signal to branch at first and second branch voltages;
- a first voltage gradient regulating circuit, connected between the first control voltage branch circuit and the first unit gain amplifier, for regulating a gradient of the first branch voltage to generate a first control signal supplied to the first unit variable gain amplifier;
- a second voltage gradient regulating circuit, connected to the first control voltage branch circuit, for regulating a gradient of the second branch voltage to generate a first gradient regulated signal;
- a second control voltage branch circuit, connected between the second voltage gradient regulating circuit and the second unit variable gain amplifier, for causing the voltage of the first gradient regulated signal to branch at second and third branch voltages, the second branch voltage being provided to the second unit variable gain amplifier as a second control signal;
- and
- a third voltage gradient regulating circuit, connected between the second control voltage branch circuit and the third unit variable gain amplifier, for regulating the gradient of the third branch voltage to generate a third control signal supplied to the third unit variable gain amplifier.
6 more elements
Dependencies are inferred from the claim text.