A transconductance amplifier mirror circuit is connected to an electrode for sensing the capacitance of the electrode with reference to ground, or the capacitance between the electrode and another electrode. A voltage level change is produced on the electrode connected to the transconductance amplifier mirror circuit to cause the transconductance amplifier mirror circuit to supply charges to or drain charges from a charge calculation circuit. The charge amount variation is converted to a signal for calculating the sensed capacitance.

An optical receiver with an expanded dynamic range for an input current is disclosed. The optical receiver includes a photodiode to generate a photocurrent, a trans-impedance amplifier (TIA) to convert the photocurrent into a voltage signal, a dummy TIA with a same arrangement as that of the TIA to generate a reference, a differential amplifier to amplify a difference between the voltage signal and the reference, a current source to extract a portion of the photocurrent, and a level detector to detect an average photocurrent and adjust the reference based on the average photocurrent.

A peak detector for a power amplifier is provided that includes a threshold voltage detector configured to pulse a detection current in response to an amplified output signal from the amplifier exceeding a peak threshold. A plurality of such peak detectors may be integrated with a corresponding plurality of power amplifiers in a transmitter. Should any peak detector assert an alarm signal or more than a threshold number of alarm signals during a given period, a controller reduces a gain for the plurality of power amplifiers.

According to one embodiment, a semiconductor device includes: a first circuit configured to drive a load couplable to a first terminal by supplying a load current to the load; and a third circuit including a second circuit configured to copy the load current based on a first voltage of the first terminal and output a first current obtained by copying the load current, the third circuit being configured to monitor a second current based on the first current. The third circuit further includes a fourth circuit configured to adjust the second current in a case where the load current is not supplied to the load.

In one example, an apparatus comprises a transistor, a switch, and a control circuit. The transistor has a first current terminal, a second current terminal, and a transistor control terminal. The switch is coupled between the transistor control terminal and a reference terminal, the switch having a switch control input. The control circuit has a control input and a control output, the control output coupled to the switch control input, and the control input coupled to at least one of the transistor control terminal, the first current terminal, or the second current terminal.