An adaptive transistor drive circuit including a multiple-emitter transistor, at least one emitter of which is connected to the drive circuit. When the drive current causes the transistor to saturate, the emitter connected to the drive circuit conducts a portion of the drive current to limit saturation of the transistor. A current source provides drive current which varies as a function of the current conducted by the collector of the transistor so as to maintain the transistor in saturation as the collector current and operating temperature vary.
In one embodiment, a method is provided for reducing output current oscillations of a driver provided with i) a current sensing circuit that senses excessive current draws of an output stage of the driver, and ii) a feedback control circuit that reduces the excessive current draws. In accordance with the method, an output of the current sensing circuit is coupled to an input of a common source amplifier with source degeneration. The output of the common source amplifier is coupled to a node between an input stage and an amplification stage of the driver. The common source amplifier is configured to be activated when the current sensing circuit senses an excessive current draw of the output stage, at which time the feedback control circuit is also activated. Related apparatus is also disclosed.
A drive circuit for a field-effect-controlled semiconductor component reduces a charging current for driving the field-effect-controlled semiconductor component when a load current limiting responds. That prevents an increase in current consumption of the drive circuit while maintaining a short switching time.
A power amplifier circuit (10) for a TDMA transmitter. The amplifier circuit (10) includes an FET amplifier (14), a current sensing resistor (24) that senses the quiescent drain current of the FET amplifier (14), and a switch (26) coupled across the sensing resistor (24). When data transmission bursts are being amplified by the amplifier circuit (10), a switch signal closes the switch (26) to bypass the sensing resistor (24) so that it does not dissipate power and reduce the efficiency of the amplifier circuit (10). When the data transmission is between data bursts, the switch signal opens the switch (26) to allow a voltage drop across the sensing resistor (24). The voltage drop is measured to determine the quiescent drain current of the FET amplifier (14) to maintain the drain current at the desirable operating point.
Efficient very low dropout (i.e., approximately equal to about V.sub.CESAT of the output transistor) dual supply voltage regulator circuits and methods are provided. The voltage regulators are capable of providing very low dropout irrespective of supply sequencing. Traditional supply sequencing problems are overcome by including an anti-latch circuit that monitors the output power supply during power-on. The anti-latch circuit is also coupled to any location in the regulator circuit where the drive current can be inhibited whenever the output power monitor senses that the output power supply is not fully operational. The anti-latch circuit operates to prevent drive current from being supplied to the output transistor unless output power is available so that the substrate of the regulator is not permitted to become forward biased (and thus prevents the establishment of an undesired latch condition).
A high frequency amplifier in which a common emitter bipolar transistor is used, and in that a constant current source and a constant voltage source are switched to apply a DC bias to a base terminal of the bipolar transistor in accordance with a power level of a high frequency signal input to the bipolar transistor or a power level of a high frequency signal output therefrom, and a frequency mixer in that a DC bias is applied to a base of at least one of a bipolar transistor for the input of a high frequency signal and a bipolar transistor for the input of a local oscillation wave by using a configuration for applying the DC bias to a base of an amplifying bipolar transistor employed in the high frequency amplifier.
