Abstract: A self-calibrating high speed D/A converter is provided with a calibration circuit for providing a fixed calibration current and a fixed calibration voltage during calibration mode, and a biasing circuit for biasing the calibration circuit with a first reference voltage and biasing the MSB and LSB array cells with a second reference voltage. By keeping the biasing voltage constant at the array cells during both calibrating and operating modes, such as 12 bits, the D/A converter effectively operates at high resolution, and at high operating speed.

Abstract: A signal coupler includes a transformer having a primary and a secondary winding. Each transformer winding has a pair of associated winding terminals and is also split at an intermediate winding position to form a pair of supplemental winding terminals. Circuitry is provided between each pair of supplemental winding terminals so as to provide different impedances in different frequency bands. In particular, a first circuit, which provides a first impedance in a first frequency range, is connected across the supplemental winding terminals of one winding. A second circuit, is connected across the supplemental winding terminals of the other transformer winding. This second circuit, in combination with the first, provides a second impedance in a second frequency range. In the disclosed embodiment, the first circuit provides an impedance of 600 ohms in the voiceband frequency range. The second circuit in combination with the first provides an impedance of 100 ohms in a frequency range extending above 40 kHz.

Abstract: An integrated circuit for squaring an original input signal includes a pair of dual-ended difference amplifiers to each of which the input signal is delivered, a pair of dual-to-single-ended converters, each receiving the respective dual-ended output of the respective difference amplifier, and a summing network for summing the squares of the outputs of the dual-to-single-ended converters. One of the dual-to-single-ended converters receives the dual-ended output of the corresponding dual-ended amplifier in opposite (cross-coupled) order from that of the other, whereby the output of the summing network is, except for an additive constant, proportional to the square of the original input signal independently of power supply voltage fluctuations within reasonable limits.