The present invention reveals a new biasing method which can be used in solid state audio power amplifier design despite of the Class of operation. The proposed biasing technology relies only on traditional electrical feedback to build up and maintain the desired biasing current and doesn't need thermal coupling or thermal tracking techniques in order to overcome power transistor device's temperature dependent input-output characteristics as required by traditional approach. An ingenious current sensing and amplification circuit is devised in order to generate an voltage output which is only corresponding to the quiescent biasing current of the output stage. This voltage output is then used as an representative of the power stage biasing current to be regulated by a feedback loop comprising a traditional voltage multiplier, the output stage and the aforementioned current sensing and amplification circuit.

An input buffer circuit may include a first switch that may couple a first voltage source to an output line based on an enable signal, such that the enable signal is configured to cause the input buffer circuit to operate. The input buffer circuit may also include a first set of switches that may couple the first voltage source to the output line based on the enable signal and an input signal, wherein the first switch and the first set of switches may couple the first voltage source to the output line in response to the input signal being greater than an input reference signal. The input buffer circuit may also include a switch that may couple a second voltage source to the output line in response to the input signal being less than the input reference signal.

The present invention reveals a new biasing method which can be used in solid state audio power amplifier design despite of the Class of operation. The proposed biasing technology relies only on traditional electrical feedback to build up and maintain the desired biasing current and doesn't need thermal coupling or thermal tracking techniques in order to overcome power transistor device's temperature dependent input-output characteristics as required by traditional approach. An ingenious current sensing and amplification circuit is devised in order to generate an voltage output which is only corresponding to the quiescent biasing current of the output stage. This voltage output is then used as an representative of the power stage biasing current to be regulated by a feedback loop comprising a traditional voltage multiplier, the output stage and the aforementioned current sensing and amplification circuit.

A transmission chain receives an incident signal to be transmitted having a first power and a first bandwidth. A first modulator frequency shifts a first signal derived from the incident signal to generate a first shifted signal at a modulation output. A power amplifier coupled to the modulation output amplifies an intermediate signal to generate an amplified output signal. A predistortion-signal-generating circuit generates, from the incident signal and from the amplified output signal in a second bandwidth that is larger than the first bandwidth, a predistortion signal having a second power lower than the first power. A second modulator frequency shifts a second signal derived from the predistortion signal to generate a second shifted signal for combination with the first shifted signal at said modulation output to produce the intermediate signal.

An apparatus for turning off a cascode amplifier having a common-base transistor and a common-emitter transistor is disclosed that includes the cascode amplifier, a feedback circuit, and a bias circuit. The feedback circuit is configured to receive a collector-voltage from the collector of the common-emitter transistor when the common-emitter transistor is switched to a first OFF state and produce a first feedback signal. The collector-voltage is equal to a emitter voltage of the common-base transistor and the collector-voltage increases in response to switching the common-emitter transistor to the first OFF state. The bias circuit is configured to receive the first feedback signal and produce a bias-voltage. A first base-voltage is produced from the bias-voltage. The cascode amplifier is configured to receive the first base-voltage and a second base-voltage. The common-base transistor is configured to switch to a second OFF state in response to receiving the second base-voltage.

A battery management system, comprising a bank of serially connected battery cells having a lower most cell connected to ground and an uppermost cell connected to one port of a load, the other port of which being connected to ground; circuitry for sampling the output voltage of a selected battery cell; a voltage to current converter for receiving the sampled battery cell output voltage, which consists of a current source that outputs current being proportional to the sampled output voltage a predetermined resistor, connected between the current source output and ground, into which the output current of the current source is fed; a control circuit, adapted to measure the voltage generated across the predetermined resistor with respect to ground; determine whether or not the selected battery cell is fully charged according to the difference between the measured voltage and a predetermined threshold voltage; repeat the process for additional battery cells of the bank.

A transmission chain receives an incident signal to be transmitted having a first power and a first bandwidth. A first modulator frequency shifts a first signal derived from the incident signal to generate a first shifted signal at a modulation output. A power amplifier coupled to the modulation output amplifies an intermediate signal to generate an amplified output signal. A predistortion-signal-generating circuit generates, from the incident signal and from the amplified output signal in a second bandwidth that is larger than the first bandwidth, a predistortion signal having a second power lower than the first power. A second modulator frequency shifts a second signal derived from the predistortion signal to generate a second shifted signal for combination with the first shifted signal at said modulation output to produce the intermediate signal.

In accordance with an embodiment, a circuit includes an amplifier and a programmable capacitor coupled between an output of the first non-inverting and the input of the first amplifier.

A junction field effect transistor (JFET) amplifier includes a first JFET gain stage having a first differential input and differential output nodes. The first JFET gain stage further includes matched first and second JFETs having gates coupled to the first differential input and terminals coupled at a common node. The first JFET gain stage also includes a current source coupled to the common node, wherein the current source includes a third JFET. The JFET amplifier further includes a second JFET gain stage having an amplifier output and a second differential input coupled to the differential output nodes.

An all-JFET operational amplifier provides improved accuracy and lower thermal drift than conventional JFET amplifiers. In some examples, the JFET operation amplifier includes an input stage including input transistors supplied with equal drain currents by matched current sources. In some examples, the input circuit is stabilized by local current feedback.