Abstract: An electronic device may have a sensor to measure ambient flicker. The sensor may be a sigma-delta converter. The flicker may be calculated based on the voltage output of the sigma-delta converter and the number of times the sigma-delta converter is triggered during a predetermined period, thereby reducing the voltage output. In particular, a fast Fourier transform (FFT) may be used on these values to determine the flicker. If desired, filtering and/or non-uniform sampling may be incorporated to avoid aliasing. Additionally or alternatively, a Lomb-Scargle spectral analysis may be used to prevent the attenuation of the measured flicker signals. As an alternative to using a sigma-delta converter to determine ambient flicker, a folding capacitive transimpedance amplifier (C-TIA) circuit or a circuit with an analog to digital converter and digital filter may be used to measure the ambient flicker.

Abstract: A switching-amplifier circuit for computer systems generates a buffered version of a received input signal. Power supply circuits coupled to the switching-amplifier circuit adjust driver power supply and driver ground supply voltage levels over respective continuous ranges of voltages based on a magnitude of the buffered signal. An output stage included in the switching-amplifier circuit generates an amplified version of the received input signal that includes a series of pulses that transition between the respective voltage ranges of the driver power supply and driver ground supply, where the respective widths or frequencies of the series of pulses encode a magnitude of the amplified version of the received input signal.

Abstract: An electronic device may have a display with an array of pixels configured to display images for a user. The electronic device may have an ambient light sensor for gathering ambient light information. The ambient light sensor may be at least partially covered by the display. The ambient light sensor may be switched into use during blanking periods when a portion of the display overlapping with the display is temporarily turned off. The ambient light sensor may include a photodetector, a first stage with an amplifier, first and second capacitors selectively coupled across the amplifier, and a second accumulation stage. During blanking time, the first capacitor may integrate photodetector current. During non-blanking, the charge stored in the first capacitor may be transferred to the second accumulation stage while the second capacitor applies an offset voltage to the photodetector to prevent undesired charge injection into the photodetector.

Abstract: An electronic device may have a display with an array of pixels configured to display images for a user. The electronic device may have an ambient light sensor for gathering ambient light information. The ambient light sensor may be at least partially covered by the display. The ambient light sensor may be switched into use during blanking periods when a portion of the display overlapping with the display is temporarily turned off. The ambient light sensor may include a photodetector, a first stage with an amplifier, first and second capacitors selectively coupled across the amplifier, and a second accumulation stage. During blanking time, the first capacitor may integrate photodetector current. During non-blanking, the charge stored in the first capacitor may be transferred to the second accumulation stage while the second capacitor applies an offset voltage to the photodetector to prevent undesired charge injection into the photodetector.

Abstract: A touch controller having noise reduction circuitry is disclosed. The touch controller can include a transmit section for generating stimulation signals to drive a touch display to sense a touch or hover event. The touch controller can also include a receive section for processing touch signals from the touch display indicative of the touch or hover event. The touch controller can reduce noise introduced into the stimulation signals and propagated through the touch display into the touch signals, thereby interfering with touch and hover sensing. To reduce the noise, the transmit section's noise reduction circuitry can isolate and subtract some or all of the noise from the stimulation signals. In addition or alternatively, the receive section's noise reduction circuitry can isolate and subtract some or all of the noise from the touch signals.

Abstract: A differential digital-to-analog converter (DAC) is disclosed. In one embodiment, a DAC includes a number of resistor networks coupled in series to form a ring, and a digital decoder configured to receive a digital code. Based on the most significant bits of the digital code, the digital decoder is configured to close selected ones of first and second groups of switches to couple first and second reference voltage nodes to corresponding tap points on the ring. Within the number of networks are first and second output circuits, each of which is arranged as a one-hot multiplexer. Based on the least significant bits of the digital code, the decoder is configured to couple respective tap points in the ring to first and second output voltage nodes in order to provide a differential output voltage based on the digital code.

Abstract: A touch controller having noise reduction circuitry is disclosed. The touch controller can include a transmit section for generating stimulation signals to drive a touch display to sense a touch or hover event. The touch controller can also include a receive section for processing touch signals from the touch display indicative of the touch or hover event. The touch controller can reduce noise introduced into the stimulation signals and propagated through the touch display into the touch signals, thereby interfering with touch and hover sensing. To reduce the noise, the transmit section's noise reduction circuitry can isolate and subtract the noise from the stimulation signals. In addition or alternatively, the receive section's noise reduction circuitry can isolate and subtract the noise from the touch signals.

Abstract: An resistor string digital-to-analog converter (DAC) that includes elements to compensate for resistor ladder loading, and/or to provide compensation for loading such as via switch current cancellation. The approach reduces output voltage sensitivity to switch resistances while also reducing INL and DNL errors. Additional resistor loops are optionally disposed at the top and bottom of one or more further segments to provide Nth order resistive current cancellation.

Abstract: A resistor string digital to analog converter formed of polysilicon resistor segments to each of which is applied an electric field. The approach improves the overall accuracy.

Abstract: A resistor string digital to analog converter formed of polysilicon resistor segments to each of which is applied an electric field. The approach improves the overall accuracy.

Abstract: An resistor string digital-to-analog converter (DAC) that includes elements to compensate for resistor ladder loading, and/or to provide compensation for loading such as via switch current cancellation. The approach reduces output voltage sensitivity to switch resistances while also reducing INL and DNL errors. Additional resistor loops are optionally disposed at the top and bottom of one or more further segments to provide Nth order resistive current cancellation.

Abstract: A bi-directional buffer includes at least a first and second pair of one-shots and transistors. At least the first pair of one-shots and the first pair of transistors enable a second input/output (I/O) terminal to follow a first I/O terminal. At least the second pair of one-shots and the second pair of transistors enable the first I/O terminal to follow the second I/O terminal. There is a detection of whether the direction of a signal is from the first I/O terminal to second I/O terminal, or vise versa. If the direction is from the first I/O terminal to the second I/O terminal, there is an at least temporarily disabling the second pair of one-shots to thereby reduce feedback that may occur from the second I/O terminal to the first I/O terminal. If the direction is from the second I/O terminal to the first I/O terminal, there is an at least temporarily disabling the first pair of one-shots to thereby reduce feedback that may occur from the first I/O terminal to the second I/O terminal.

Abstract: A bi-directional buffer includes at least a first and second pair of one-shots and transistors. At least the first pair of one-shots and the first pair of transistors enable a second input/output (I/O) terminal to follow a first I/O terminal. At least the second pair of one-shots and the second pair of transistors enable the first I/O terminal to follow the second I/O terminal. There is a detection of whether the direction of a signal is from the first I/O terminal to second I/O terminal, or vise versa. If the direction is from the first I/O terminal to the second I/O terminal, there is an at least temporarily disabling the second pair of one-shots to thereby reduce feedback that may occur from the second I/O terminal to the first I/O terminal. If the direction is from the second I/O terminal to the first I/O terminal, there is an at least temporarily disabling the first pair of one-shots to thereby reduce feedback that may occur from the first I/O terminal to the second I/O terminal.

Abstract: A low voltage constant transconductance input stage is achieved with relatively simple design methodology. The approach uses current-mode techniques and is based upon the processing of signal currents, rather than handling the bias currents of input stages. Such an approach becomes universal and independent of the input stage transistor types (FET or bipolar) and their operating regions. Further, the arrangement considerably simplifies the design procedure of low voltage operational amplifiers. MOS and bipolar Op Amp input stages are described wherein almost constant g.sub.m is achieved which is independent of the common mode input voltage ranging from rail-to-rail.