| 摘要 |
A cascode amplifier which includes a cascode amplifier stage, an output node (coupled directly or indirectly to the cascade amplifier stage), and positive feedback circuitry coupled between the output node and the cascade amplifier stage (or positive feedforward circuitry coupled between the input node and the cascode amplifier stage) for improved amplifier response to rapidly varying input. Preferably, the amplifier is implemented as an integrated circuit or portion of an integrated circuit, and the feedback or feedforward circuitry is configured to reduce rise times and fall times of the output potential (in response to falling and rising edges of the input) to within acceptable limits, with no more than acceptably small overshoot at both the rising and falling edges of the output potential, and with at least substantially equal overshoot at both the rising and falling edges of the output potential. Preferably, the feedback circuitry is configured to provide relatively less positive feedback to the cascode amplifier stage at each rising edge of the output than at each falling edge of the output, with the feedback preferably being a feedback current that flows to or from a capacitor coupled to the output node. Preferably, the feedback circuitry steers away from the cascode amplifier stage a portion of a feedback current while the output rises and steers no part of the feedback current away from the cascode amplifier stage while the output falls. Other aspects of the invention are methods for operating such an amplifier, and for designing such an amplifier to have optimized response to a rapidly varying input.
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