Abstract: A cascode stage is arranged to improve performance of an operational amplifier. The cascode stage includes transistors that are arranged to operate as a current mirror. Each side of the current mirror has a corresponding voltage at a corresponding node. One of the corresponding nodes corresponds to a high impedance node that is coupled to a subsequent stage of the amplifier. The voltages at the corresponding nodes are closely matched to one another such that the input referred offset in the amplifier is minimized and the power supply rejection ratio is improved (PSRR). A transistor threshold voltage and a transistor saturation voltage determine the headroom requirements of the cascode stage, such that low power supply voltage operation is possible. The biasing of the transistors in the cascode stage is simplified such that minimal biasing circuitry is required, and overall power consumption may be minimized.

Abstract: A circuit for countering offset voltage in an amplifier induced by changes in the output load. The circuit comprises an input stage, an output stage, and first and second current compensation stages. The first current compensation stage is coupled to the output stage and produces a first compensation current that is a function of the output current. The input stage is coupled to the first current compensation stage from which it receives the first compensation current. The input stage is configured to cause a change in the voltage between its input terminals in response to the first compensation current. The second current compensation stage produces a second compensation current, which is also fed into the input stage to act jointly with the first compensation current. The first compensation current may be linearly related to the output current. The second compensation current may be exponentially related to the output current.

Abstract: A temperature stabilized, constant current source capable of charging a fully discharged battery of the present invention includes a feedback control stage that provides a substantially constant battery charging current at a particular temperature. A temperature stabilized current source stage coupled to a bias resistor includes a negative temperature coefficient current source that provides a countervailing control current to a positive temperature coefficient current source that is coupled from a sensing resistor. The temperature dependencies of the positive and negative temperature coefficient current sources tend to cancel each other out so as to provide a temperature stabilized current to the sensing resistor. The bias resistor provides a bias current to the temperature stabilized current source stage in such a way that the temperature stabilized current source stage provides a charging current to a fully discharged battery.

Abstract: A differential input stage with full-rail sensing and reduced latch-up susceptibility includes an emitter-coupled pair, a current mirror, and several series resistors. For a NPN emitter-coupled pair, a series resistor is connected between the input node and the base of each transistor of the emitter-coupled pair, and a series resistor is connected between each load resistor and its corresponding current mirror transistor. The series resistors reduce current flowing into the PN junctions when power to the overall circuit is disabled but an input signal is present at the input terminals.

Abstract: An amplifier input stage having a constant input gm and including first and second differential transistor pair so as to provide operation with inputs at or near the upper and lower power supply rails. A comparator circuit operates to control which of the transistor pair is active based upon the relative magnitudes of the amplifier input stage inputs and a reference voltage.

Abstract: A temperature stabilized, constant current source of the present invention includes a feedback control stage that provides a substantially constant battery charging current at a particular temperature. A temperature stabilized current source stage includes a negative temperature coefficient current source that provides a countervailing control current to a positive temperature coefficient current source that is coupled from a sensing resistor. The temperature dependencies of the positive and negative temperature coefficient current sources tend to cancel each other out so as to provide a temperature stabilized current to the sensing resistor. In this way, a control voltage is developed across the control resistor that is independent of resistor temperature dependencies.