Abstract: A power amplifier comprises first and second power transistor stages that receive first and second supply voltages, respectively. First and second bias circuits provide the biasing for the first and second power transistor stages, respectively, in response to a reference voltage and a bias voltage.

Abstract: A method for monitoring the pH of a patient includes the step of providing a magnetic resonance system having a magnet with a bore configured to receive a portion of a finger of a patient without receiving a substantially larger portion of the body of the patient. The method proceeds by inserting the finger of the patient into the bore of the magnet and monitoring the pH level of capillary bed tissue in the finger with the magnetic resonance system. Preferably, the system is configured to monitor the spectrum of phosphorus-31 metabolites in the finger and produce information in the form of a normalized phosphorous integral ratio indicative of the spectral area in order to alert an operator of the occurrence of a condition in which the normalized phosphorous integral ratio is greater than one in the setting of decreasing pH, as indicative of capillary bed tissue shock--lactic acidosis.

Abstract: The present invention is directed to a voltage controlled single-package integrated circuit device, capable of thermal compensation, for biasing a quasi-linear bipolar device. The bias circuit also provides a low impedance source to a RF device so that the bias point does not dynamically change with the RF signal, thus improving linearity. Changes in the base-emitter voltage level of the RF device are monitored by a reference diode to provide automatic temperature compensation. The reference diode is in close thermal proximity to the RF device, allowing for accurate thermal tracking. The base-emitter voltage may be electronically adjusted by means of a control voltage input, such being suitable for hook-up to a computer system having a digital to analog convertor thereby allowing for fine voltage adjustments. The control voltage may also be used to adjust the class of operation of the RF device or provide external temperature control.

Abstract: Linear high gain (greater than 20 dB) and high power (greater than +20 dbm) devices for RF power amplifiers are achieved using either fully monolithic or hybridized versions of silicon MMIC two-stage cascaded amplifiers. The device features three feedback loops in conjunction with a DC biasing network. Resistor-capacitor feedback circuits utilize only two capacitive elements which are provided as a single three-terminal element having a common lower plate.

Abstract: A controlled-output amplifier is provided whose output power level may be set to any of a number of predetermined levels and maintained substantially constant. The amplifier includes a detector which senses the output power level and produces a signal indicative of the magnitude thereof. The detector includes a single detector diode which may be biased to any of a number of preselected bias states by a bias control unit. The bias control unit increases the dynamic range of the detector diode while eliminating the need for a conventional temperature compensation diode.