Output Buffer Slew Rate Control Without Extra Current Draw
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Solution Overview
Problem
Conventional output buffer circuits face challenges in achieving high slew rate without increasing current consumption and often experience short circuit currents due to coupling effects during slew rate boosting operations.
Innovation Solution
An output buffer circuit design that includes a slew rate control circuit with diode-connected driver transistors and a driver control circuit with switches and compensation capacitors, which selectively boosts slew rate based on potential differences and prevents short circuit currents by managing power supply connections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the current consumption of the amplifier is increased to achieve high slew rate, then the slew rate performance is improved, but the current consumption increases which makes it difficult to apply to portable electronic devices
Solution Approach 1:
The amplifier dynamically adjusts its operating current based on the slew rate requirement. During normal operation, the amplifier operates at low current consumption. When a high slew rate is needed (detected through potential difference between input and output signals), the amplifier temporarily increases current by activating additional current paths through the driver transistors, then returns to low current mode afterward. This dynamic adjustment resolves the contradiction between maintaining high slew rate capability and minimizing average current consumption.
2Speed
If the slew rate is boosted by conventional output buffer circuits, then the slew rate is improved, but short circuit current occurs due to coupling effect from compensation capacitor
Solution Approach 1:
The circuit performs preliminary action by pre-charging or pre-discharging the compensation capacitor through controlled current paths before the main slew rate boosting operation. The driver control circuit detects the potential difference between input and output signals and activates specific current paths in advance to prepare the compensation capacitor, preventing the coupling effect that would otherwise cause short circuit current during the slew rate boost. This preliminary preparation eliminates the harmful short circuit current while maintaining the beneficial high slew rate performance.
Data Source
AI summary
An output buffer circuit is disclosed to achieve a high slew rate without increasing current consumption. The output buffer circuit includes an input circuit configured to output a first signal and a second signal in response to an input signal, and a slew rate control circuit configured to connect one of the first signal and the second signal to an output terminal to control a slew rate of an output signal based on or in response to a potential difference between the input signal and the output signal.