摘要:
A reference voltage generator includes a voltage generation circuit, an amplifier, a diode unit and a transistor. The voltage generation circuit includes an output terminal for outputting a reference voltage, a first terminal having an operational voltage, and a second terminal. The amplifier includes an input terminal coupled to the first terminal of the voltage generation circuit, an output terminal, a first terminal coupled to a first voltage terminal, and a second terminal. The diode unit includes a first terminal coupled to the second terminal of the amplifier, and a second terminal coupled to the second terminal of the voltage generation circuit and a second voltage terminal. The transistor includes a first terminal coupled to the first terminal of the amplifier, a second terminal coupled to the output terminal of the voltage generation circuit, and a control terminal coupled to the output terminal of the amplifier.
摘要:
Example current tracking circuits and systems as well as methods for tracking current are described herein. In one example, a current tracking circuit comprises a current mirror that receives a power supply input and a control signal as inputs, wherein the current mirror has a mirror ratio. The current tracking circuit also comprises a programmability sub-circuit coupled to the current mirror that trims a value of the mirror ratio. In another example, a method comprises performing current mirroring using a current mirror comprising a sense device, wherein a mirror ratio of the current mirror is based on a programmable sub-circuit. The method further comprises maintaining, by a voltage regulation loop, a collector potential of the sense device within a threshold difference level of a collector potential of a power device coupled to the sense device, wherein the sense device mirrors a current flowing in the power device.
摘要:
A voltage reference circuit includes a bipolar transistor and a circuit configured to measure the ratio of emitter current to base current of the bipolar transistor. The output voltage of the voltage reference circuit is compensated as a function of the measured ratio.
摘要:
Example current tracking circuits and systems as well as methods for tracking current are described herein. In one example, a current tracking circuit comprises a current mirror that receives a power supply input and a control signal as inputs, wherein the current mirror has a mirror ratio. The current tracking circuit also comprises a programmability sub-circuit coupled to the current mirror that trims a value of the mirror ratio. In another example, a method comprises performing current mirroring using a current mirror comprising a sense device, wherein a mirror ratio of the current mirror is based on a programmable sub-circuit. The method further comprises maintaining, by a voltage regulation loop, a collector potential of the sense device within a threshold difference level of a collector potential of a power device coupled to the sense device, wherein the sense device mirrors a current flowing in the power device.
摘要:
Several methods to obtain process insensitive base-emitter forward voltage of a transistor are described. The main concept is to recognize that the transistor current gain is the parameter that affects this voltage the most with normal process variations. The use of transistor driven with known base current removes this error. In alternative, a method for compensating the base-emitter forward voltage variations is described. This is applicable to analog integrated circuits that utilize the base-emitter forward voltage of a transistor and in particular in applications that make use of either accurate voltage references, thermal sensing elements, solid state thermostats and very common thermal shutdown protection circuits.
摘要:
A power supply device produces a predetermined voltage from a supply voltage through a voltage follower composed of a plurality of transistors. The voltage follower has a function of preventing backflow current. The voltage follower has one end connected to the supply voltage and another end connected to a capacitor. A constant voltage generating circuit produces a constant voltage from the voltage across the capacitor. A switch circuit is connected between the supply voltage and the control electrode of one of the transistors constituting the voltage follower other than the first-stage transistor thereof. A voltage drop detecting circuit detects a drop below a predetermined level in the voltage across the capacitor, and turns on the switch circuit on detecting such a drop.
摘要:
A pull-down circuit uses an npn transistor operating at close to saturation and the collector/emitter voltage is used as the pull-down voltage. To keep this within strict limits the npn transistor is connected in circuit with other transistors and resistors as well as a current source that generates a current proportional to absolute temperature. By selecting the values of the resistors and transistor parameters the collector/emitter voltage may be kept stable within a small range over wide temperature variation.
摘要:
An RMS-DC converter provides extended dynamic range by driving a squaring cell with a variable gain amplifier. Temperature effects in the squaring cell can be cancelled by driving a second squaring cell with a reference signal and averaging the difference between the output signals from the two squaring cells. In a transmission system utilizing a power measurement system having two detector cells, square-law conformance errors in the detector cells can be cancelled by driving one of the detectors cells with a replica of the baseband modulation signal.
摘要:
A system includes a first power supply line that is associated with a first voltage level and a second power supply line that is associated with a second voltage level. A power supply is coupled to the first and second power lines to establish a first voltage of the first power supply line near the first voltage level and a second voltage of the second power supply line near the second voltage level. The power supply has a response during a time period after the activation or deactivation of the power supply in which the power supply does not maintain a difference between the first and second voltages within a predefined range. The system includes a circuit that is coupled to the first and second power supply lines to maintain the difference between the first and second voltages within the predefined range during the time period.
摘要:
A current source circuit for providing a stable current into a filter element of a phase-lock-loop circuit of a clock generator. The current source circuit comprises a first resistor coupled to a voltage supply. The emitter of a first transistor is coupled to the first resistor; the base is coupled to a bias voltage, and the collector is coupled to a capacitor. The capacitor forms part of the filter of the phase-lock-loop circuit. Current flows from the voltage supply through the first resistor and first transistor into the capacitor. A second transistor has a collector coupled to the capacitor; a base; and an emitter coupled to ground via a second resistor. The second transistor and resistor causes a fixed amount of current to be sinked from the capacitor. Leakage current flowing out of the capacitor due to the inherent Rcb impedance associated with the second transistor is directed to a path provided by a third transistor. The third transistor has an emitter coupled to the base of the second transistor and a collector coupled to the emitter of the first transistor. The third transistor directs the Rcb leakage current inherent to the second transistor back into the capacitor. Thereby, the Rcb leakage current flowing out from the capacitor is canceled by the current flowing back into the capacitor via the third and first transistors. This produces a more stable current, and hence, more stable voltage being maintained by the capacitor. A more stable voltage means that the capacitor can be made smaller. In turn, this enables the phase-lock-loop to be fabricated on-chip with the rest of the clock generator, thereby minimizing its susceptibility to external noise and interferences. Furthermore, a more stable voltage across the filter element of the phase-lock-loop reduces unwanted jitter in the clock signal.