A protection circuit comprises a first transistor, a comparator, a second transistor, and a third transistor. The first transistor has a gate connected to an input terminal and configured to pass a drain current based on a potential at the input terminal. The comparator has a non-inverting terminal to which a source of the first transistor is connected and an inverting terminal to which a reference voltage is applied. The second transistor has a gate to which an output of the comparator is applied, a source connected to a power supply voltage, and a drain connected to the input terminal. The third transistor has a gate to which a predetermined voltage is applied, a drain connected to the gate of the second transistor, and a source connected to the drain of the input transistor.

A wide voltage trans-impedance amplifier includes a first P-channel metal oxide semiconductor (PMOS) transistor PM1, a second PMOS transistor PM2, a third PMOS transistor PM3, a fourth PMOS transistor PM4, a fifth PMOS transistor PM5, a first bias voltage VB1, a second bias voltage VB2, a third bias voltage VB3, a first N-channel metal oxide semiconductor (NMOS) transistor NM1, and a second NMOS transistor NM2. A common-gate amplifier detects a change of an input voltage, and a negative feedback is constructed by injecting a current into a current mirror to achieve a low input impedance. The trans-impedance amplifier uses a common-gate amplifier to monitor an input voltage and uses a current mirror to perform the transconductance enhancement on an input transistor, while ensuring a relatively high loop gain.

A second main electrode of a first transistor is connected to a first main electrode of a sixth transistor, a second main electrode of the sixth transistor is connected to a first main electrode of a fifth transistor at a first node, a second main electrode of the fifth transistor is connected to a second main electrode of a second transistor, a control electrode of the fifth transistor is connected to the second main electrode of the fifth transistor, a second main electrode of a third transistor is connected to a first main electrode of a fourth transistor at a second node, and a control electrode of the fourth transistor is connected to the control electrode of the fifth transistor. A gain control amplifier controls a voltage supplied to a control electrode of the sixth transistor such that the first node and the second node are equal in voltage.

A second main electrode of a first transistor is connected to a first main electrode of a sixth transistor, a second main electrode of the sixth transistor is connected to a first main electrode of a fifth transistor at a first node, a second main electrode of the fifth transistor is connected to a second main electrode of a second transistor, a control electrode of the fifth transistor is connected to the second main electrode of the fifth transistor, a second main electrode of a third transistor is connected to a first main electrode of a fourth transistor at a second node, and a control electrode of the fourth transistor is connected to the control electrode of the fifth transistor. A gain control amplifier controls a voltage supplied to a control electrode of the sixth transistor such that the first node and the second node are equal in voltage.

A power supply includes a voltage regulator, a transistor, a current-to-voltage transform circuit, and a comparator. The voltage regulator receives a control signal, a source voltage, and a control voltage, and outputs a supply voltage according to the control voltage and the control signal. The transistor has a first terminal receiving the source voltage, and a control terminal coupled to the voltage regulator. The current-to-voltage transform circuit has a first terminal coupled to a second terminal of the transistor, a second terminal for receiving a reference voltage. The comparator has a first input terminal for receiving a comparison signal, a second input terminal coupled to the first terminal of the current-to-voltage transform circuit, and an output terminal for outputting the control voltage.

A power supply includes a voltage regulator, a transistor, a current-to-voltage transform circuit, and a comparator. The voltage regulator receives a control signal, a source voltage, and a control voltage, and outputs a supply voltage according to the control voltage and the control signal. The transistor has a first terminal receiving the source voltage, and a control terminal coupled to the voltage regulator. The current-to-voltage transform circuit has a first terminal coupled to a second terminal of the transistor, a second terminal for receiving a reference voltage. The comparator has a first input terminal for receiving a comparison signal, a second input terminal coupled to the first terminal of the current-to-voltage transform circuit, and an output terminal for outputting the control voltage.

A linear regulator with indirect leakage compensation is presented. The regulator has a pass device coupled between an input voltage and an output node, a feedback loop for controlling the pass device based on a reference voltage and a feedback voltage that depends on an output voltage, an off-state device that is kept in the off-state, and a leakage compensation circuit for sinking a leakage compensation current from the output node, in dependence on a leakage current of the off-state device. The off-state device is coupled between the leakage compensation circuit and an intermediate voltage level of the linear regulator. The intermediate voltage level is a voltage level between the input voltage level and ground, with a magnitude of the intermediate voltage level being smaller than a magnitude of the input voltage level. A corresponding method of operating a linear regulator with leakage compensation is presented.

A common source preamplifier for a MEMS capacitive sensor is disclosed. The preamplifier is a single-stage amplifier employing negative feedback. The preamplifier provides stable gain independent of temperature and at the same time provides effective buffering for a subsequent stage. Further, the preamplifier may be configured to provide different values of gain. Furthermore, the preamplifier has lower noise and consumes lesser area and lesser power than prior art.

Variations in a receiving circuit employing differential signaling are reduced. The receiving circuit converts a first signal and a second signal which are supplied through differential signaling into a third signal which is a single-ended signal and outputs the third signal. The receiving circuit includes an operational amplifier, a first element, a first transistor, and a first circuit. The first element is connected to the first circuit through a first node to which the first transistor is connected. The first signal and the second signal that is the inverse of the first signal are supplied to the operational amplifier. The operational amplifier supplies an output signal to the first element, and a first preset potential is supplied to the first node through the first transistor. A signal including variations of the operational amplifier is stored in the first element in accordance with the first preset potential. The first circuit that is supplied with the first preset potential determines an initial value of the third signal without being influenced by the signal including variations of the operational amplifier.

A current regulator and a method for regulating a current flowing through a device such as a semiconductor light source is presented. The current regulator has a voltage controller coupled to a current steering circuit. The voltage controller is adapted to operate the current steering circuit in a linear mode.