A new circuit to compute a continuous-time derivative is introduced. Comprising only one capacitor and six to eight transistors, this derivative circuit occupies very little real estate and consumes limited power, making it particularly well suited to low-power and array applications such as imager systems and sub-banded audio-processing applications. A description of the operation of this circuit is provided along with results from a circuit fabricated in a standard 0.5 mm CMOS process.Introduction: Determining how a signal pattern varies over time is important for many perceptual and sensory processing applications. For example, temporal derivatives are used for motion detection within pixel arrays [1, 2] and for speech processing on sub-banded audio signals [3,4]. Such applications are often implemented in continuoustime circuits to realise low-power implementations and local processing on the sensor data. In this Letter, we provide a description of the design criteria of 'frequency-normalised' continuous-time derivative circuits. We then present a novel derivative circuit that is electronically tunable and that is well suited to array-processing systems, such as the aforementioned examples, owing to its extremely compact size and low-power operation. Results are provided from a circuit fabricated in a standard 0.5 mm CMOS process.

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