Abstract: A differential stage that provides minimal offset between its differential inputs includes first and second transistor sets and first and second buffering elements. Each transistor of the first and second transistor sets includes an input terminal, a common terminal, and an output terminal. The differential inputs are provided by the input terminals of the transistors in the second transistor set via the second buffering element. An output of the differential stage is provided by the coupling between the first and second buffering elements.

Abstract: A voltage multiplier includes input and output differential multiplying stages, first and second operational amplifiers, and first and second linear devices. An input voltage is received by an inverting input of the first operational amplifier via the first linear device. An output of the voltage multiplier is provided at an output of the second operational amplifier. When the voltage multiplier is disabled, the second linear device provides the input voltage a linear path to an inverting input of the second operational amplifier and, when the voltage multiplier is operational, the second linear device has negligible effect on the voltage multiplier.

Abstract: A circuit that combines the functions of audio compression and voice detection comprises an amplifier in a negative-feedback configuration in which the feedback signal is the product of the output of the amplifier and a syllabic voltage derived from that output. The syllabic voltage is compared with a threshold level to provide an output that is a measure of the presence of a voice signal. In an alternate embodiment, the syllabic voltage is compared with the sum of a threshold level and a detected syllabic voltage to generate a signal that is a measure of the presence of voice. The syllabic detector may be either an averaging detector or a valley detector.