Abstract: The present invention is an apparatus and method to provide a high supply rejection and a full rail-to-rail output swing in an amplifier circuit. A first stage generates a first output. The first stage is powered by a second supply. A second stage is coupled to the first stage to generate an amplifier output. The second stage is powered by a first supply. The first and second supplies are different in regulation mode. By making the second supply a low noise supply, the power supply noise amplified by the first stage is minimized, with the voltage gain of the second stage regaining the rail-to-rail swing lost by the first stage due to the regulator supplying very low noise power to the first stage.

Abstract: Operational amplifiers with a gain enhancement apparatus and method result in a substantial improvement in the gain of such amplifiers without change in the gain of the signal amplifying transistors. The gain enhancement is achieved by providing a circuit for having one transistor in the folded cascode stage of the amplifier substantially track the operating conditions of another transistor in the folded cascode stage, thereby substantially eliminating the unbalanced differential drive from the differential input stage that would have been required to accommodate the Early effect in the second stage. This is particularly advantageous when driving MOS output drivers wherein large voltage excursions in the second stage are required, particularly when sinking current from a load.

Abstract: An amplifier circuit that offers high bandwidth operation and a high slew rate is disclosed. The amplifier circuit may also have an input voltage swing down to the negative rail which is particularly suitable for low voltage applications having a single power source. In one embodiment, the amplifier circuit amplifies a difference voltage between first and second input voltages to produce an output voltage, and includes: an analog voltage-to-current converter for receiving the first and second input voltages and producing complementary current signals; and a complementary mirror output stage coupled to receive the complementary current signals at respective mirror circuits.

Abstract: A circuit for controllably coupling an input to an output. The circuit includes: (1) a pass transistor having an emitter, a collector and a base, the emitter being coupled to the input, the collector being coupled to the output; (2) a second transistor coupled to the pass transistor, and biased to operate with a collector-to-base voltage approximately equal to zero; and (3) a control circuit coupled to the input, the output and the base of the pass transistor, the control circuit controllably turning the pass transistor on. When the pass transistor is turned on, the control circuit maintains in the pass transistor a collector current approximately equal to a predetermined scale factor times the collector current of the second transistor. The predetermined scale factor ensures that the pass transistor operates at the edge of a saturation region when the pass transistor is turned on.

Abstract: Three state high speed amplifiers having a high output impedance when disabled and a minimum glitch when enabled and disabled. The amplifiers utilize complementary emitter followers for the output stage. When the amplifiers are disabled, circuitry provided for the purpose drives is responsive to the voltage on the output of the amplifier to maintain the base-emitter voltages of the output emitter followers at a substantially constant level below the turn-on voltages of the transistors, such as substantially zero volts. When the amplifier is enabled, the circuitry is also responsive to the voltage on the output of the amplifier, but this time to allow the base-emitter voltages of the output emitter followers to at least freely rise to the turn-on voltages of the transistors.

Abstract: A multi-stage current feedback amplifier having a first stage and a second stage. The multi-stage amplifier comprises a transistor device having a base, an emitter, and a collector, as well as a replicating device having a base, an emitter, and a collector. The base of the replicating device is coupled to the base of the transistor device, wherein a voltage in the emitter of the transistor device is substantially replicated in the emitter of the replicating device. Further, the inventive multi-stage feedback amplifier comprises a current mirror circuit having a current mirror circuit input and a current mirror circuit output, which current mirror circuit input is coupled to the collector of the replicating device. The current mirror circuit output is coupled to the collector of the transistor device.

Abstract: A DC--DC converter capable of both step-up and step-down operations includes a synchronous rectifier coupled between a rectifier connection and an output node, an inductor coupled between an input node and the rectifier connection, a rectifier control circuit for controlling the synchronous rectifier, the rectifier control circuit coupled to the input node, to the synchronous rectifier, to the rectifier connection and to the output node, and a switch coupled between the rectifier connection and ground. After closing the switch to build up energy in the inductor, the synchronous rectifier turns on simultaneously with the opening of the switch when the voltage of the rectifier connection is greater than the voltage of the output node and the voltage of the input node. The synchronous rectifier turns off when a current through the inductor becomes zero or when the switch closes again.

Abstract: A simple high speed precision transconductance amplifier circuit having a low offset. The circuit uses as an input stage two substantially identical transistors of a first conductivity type connected in series so as to have the same current there through, neglecting base currents. A second stage uses two substantially identical transistors of a second conductivity type connected in series, with the output of the amplifier being a current mirrored from the second stage. The offset is maintained low by maintaining the V.sub.BE of the transistors in the two stages substantially identical by connecting together the base and collector of one of the transistors in one stage and coupling the resulting V.sub.BE of the transistor so coupled to one of the transistors of opposite conductivity type in the other stage. Various embodiments and variations are disclosed.

Abstract: A high input impedance common-emitter amplifier stage is disclosed. This amplifier stage utilizes a transistor to buffer the base drive from the input stage of a Darlington circuit. This buffer action increases the input impedance of the common-emitter stage by a factor of beta (.beta.) of the buffering transistor. Various embodiments are disclosed.

Abstract: A simple high speed precision transconductance amplifier circuit having a low offset. The circuit uses as an input stage two substantially identical transistors of a first conductivity type connected in series so as to have the same current there through, neglecting base currents. A second stage uses two substantially identical transistors of a second conductivity type connected in series, with the output of the amplifier being a current mirrored from the second stage. The offset is maintained low by maintaining the V.sub.BE of the transistors in the two stages substantially identical by connecting together the base and collector of one of the transistors in one stage and coupling the resulting V.sub.BE of the transistor so coupled to one of the transistors of opposite conductivity type in the other stage. Various embodiments and variations are disclosed.