Abstract: A system and method for demodulating amplitude modulated input signals uses two comparators and a charge pump circuit, which is positioned between the two comparators, to produce a demodulated signal of an amplitude modulated input signal. The two comparators and the charge pump circuit form a demodulating unit that may be a part of an infrared remote control receiver. The first comparator converts the input signal from a waveform to a pulse form. The charge pump circuit then converts the pulse signal into an integrated signal in a triangular pulse form. The second comparator converts the integrated signal from a triangular pulse form to a rectangular pulse form to produce the demodulated signal.

Abstract: A fast-settling digital automatic gain control circuit comprises first and second gain-controllable amplifiers in series. Each amplifier can be digitally switched between minimum and maximum gains by control logic that receives inputs from a multi-level voltage comparator. A peak detector connected to the output of the first gain-controlled amplifier is used to set the overall operating ranges for several threshold detectors. Four reference voltages are generated from the peak detector. The highest reference voltage is used to clock and reset the gain control logic with a hysteresis comparator to the instantaneous input signal from the first gain-controlled amplifier. The three other lower reference voltages are used to provide three-bits of digital input data to the gain control logic. Two digital controls are output, a min/max gain bit for the first gain-controlled amplifier, and a similar min/max gain bit for the second gain-controlled amplifier.

Abstract: An optical receiver has a voltage supply, a first node, and a second node. A first input of a differential amplifier is coupled to the first node and a second input of the differential amplifier is coupled to the second node. A photodetector is coupled between the voltage supply and the first node, which produces a photodetector capacitance. A programmable variable capacitor having a capacitance selectively matched to the photodetector capacitance is coupled between the voltage supply and the second node.

Abstract: A bandgap circuit includes a current mirror that generates a proportional to absolute temperature current at an output node that outputs the bandgap reference voltage. A first current path including a first resistor is coupled between the output node and a first bipolar transistor. The second current path including a second resistor is coupled between the output node and a second bipolar transistor. The first current path is parallel to the second current path. The circuit outputs a bandgap reference voltage.

Abstract: A circuit that protects against electrostatic discharge and electrical over stress is provided. The circuit includes a first transistor including a substrate. An internal predetermined voltage source biases the substrate of the first transistor. The internal predetermined voltage source is greater than or equal to a source voltage provided to a source of the first transistor and isolates a substrate voltage of the first transistor from a supply voltage of the circuit. A first resistor is coupled to a gate of the first transistor and ground. The circuit also includes a zener diode coupled between ground and the supply voltage of the circuit. The zener diode shorts to ground if the supply voltage of the circuit exceeds the breakdown voltage of the zener diode.

Abstract: An optical receiver includes a photodetector coupled to a gain section having a variable gain stage. The gain stage provides an output voltage signal. A digital automatic gain control circuit is coupled to the output voltage signal and provides a digital output value to at least the variable gain stage. The gain of the variable gain stage is set according to the digital output value.

Abstract: A circuit has a voltage source, a node, a photodiode electrically coupled between the voltage source and the node, a voltage reference, a resistor electrically coupled between the node and the voltage reference, and a voltage clamp electrically connected to the node.

Abstract: In one embodiment, an optical transducer, such as an infrared transducer, generates an output signal that is representative of optical irradiance. A noise control circuit is coupled in a power supply path of the optical transducer. A switching circuit varies the noise control provided by the noise control circuit, in response to changes in the output signal of the optical transducer. The noise control may be varied in a number of different ways, including: turning the noise control on or off, varying the noise control in discrete steps, or varying the noise control in a continuous manner. Methods for varying noise control in response to optical irradiance of an optical transducer are also disclosed.