Photodiodes can be broken into two categories: largearea photodiodes with their attendant high capacitance(30pF to 3000pF) and smaller area photodiodes withrelatively low capacitance (10pF or less). For optimalsignal-to-noise performance, a transimpedance amplifi erconsisting of an inverting op amp and a feedback resistoris most commonly used to convert the photodiode currentinto voltage. In low noise amplifi er design, large areaphotodiode amplifi ers require more attention to reducingop amp INPUT voltage noise, while small area photodiodeamplifi ers require more attention to reducing op amp INPUTcurrent noise and parasitic capacitances.
High INPUT impedance and a wide INPUT range are twohighly desirable features in a precision analog-to-digitalconverter, and the LTC®2449 delta-sigma ADC has both.With just a few external components, the LTC2449 formsan exceptional measurement system with very high INPUTimpedance and an INPUT range that extends 300mV beyondthe supply rails.
A fully differential amplifi er is often used to converta single-ended signal to a differential signal, a designwhich requires three signifi cant considerations: theimpedance of the single-ended source must match thesingle-ended impedance of the differential amplifi er,the amplifi er’s INPUTs must remain within the commonmode voltage limits and the INPUT signal must be levelshifted to a signal that is centered at the desired outputcommon mode voltage.
The MAX2691 low-noise amplifier (LNA) is designed forGPS L2 applications. Designed in Maxim’s advancedSiGe process, the device achieves high gain andlow noise figure while maximizing the INPUT-referred 1dBcompression point and the 3rd-order intercept point. TheMAX2691 provides a high gain of 17.5dB and sub 1dBnoise figure.
Differential Nonlinearity: Ideally, any two adjacent digitalcodes correspond to output analog voltages that are exactlyone LSB apart. Differential non-linearity is a measure of theworst case deviation from the ideal 1 LSB step. For example,a DAC with a 1.5 LSB output change for a 1 LSB digital codechange exhibits 1⁄2 LSB differential non-linearity. Differentialnon-linearity may be expressed in fractional bits or as a percentageof full scale. A differential non-linearity greater than1 LSB will lead to a non-monotonic transfer function in aDAC.Gain Error (Full Scale Error): The difference between theoutput voltage (or current) with full scale INPUT code and theideal voltage (or current) that should exist with a full scale INPUTcode.Gain Temperature Coefficient (Full Scale TemperatureCoefficient): Change in gain error divided by change in temperature.Usually expressed in parts per million per degreeCelsius (ppm/°C).Integral Nonlinearity (Linearity Error): Worst case deviationfrom the line between the endpoints (zero and full scale).Can be expressed as a percentage of full scale or in fractionof an LSB.LSB (Lease-Significant Bit): In a binary coded system thisis the bit that carries the smallest value or weight. Its value isthe full scale voltage (or current) divided by 2n, where n is theresolution of the converter.Monotonicity: A monotonic function has a slope whose signdoes not change. A monotonic DAC has an output thatchanges in the same direction (or remains constant) for eachincrease in the INPUT code. the converse is true for decreasing codes.
ANALOG INPUT BANDWIDTH is a measure of the frequencyat which the reconstructed output fundamental drops3 dB below its low frequency value for a full scale INPUT. Thetest is performed with fIN equal to 100 kHz plus integer multiplesof fCLK. The INPUT frequency at which the output is −3dB relative to the low frequency INPUT signal is the full powerbandwidth.APERTURE JITTER is the variation in aperture delay fromsample to sample. Aperture jitter shows up as INPUT noise.APERTURE DELAY See Sampling Delay.BOTTOM OFFSET is the difference between the INPUT voltagethat just causes the output code to transition to the firstcode and the negative reference voltage. Bottom Offset isdefined as EOB = VZT–VRB, where VZT is the first code transitionINPUT voltage and VRB is the lower reference voltage.Note that this is different from the normal Zero Scale Error.CONVERSION LATENCY See PIPELINE DELAY.CONVERSION TIME is the time required for a completemeasurement by an analog-to-digital converter. Since theConversion Time does not include acquisition time, multiplexerset up time, or other elements of a complete conversioncycle, the conversion time may be less than theThroughput Time.DC COMMON-MODE ERROR is a specification which appliesto ADCs with differential INPUTs. It is the change in theoutput code that occurs when the analog voltages on the twoINPUTs are changed by an equal amount. It is usually expressed in LSBs.
This reference design (RD) features a fullyassembled and tested surface-mount printed circuitboard (PCB). The RD board utilizes the MAX48851:2 or 2:1 multiplexer and other ICs to implement acomplete video graphics array (VGA) 8:1multiplexer.VGA INPUT/output connections are provided to easilyinterface the MAX4885 RD board with VGAcompatibledevices. The RD board gives the optionto use a single 5V DC power supply (V+), or this RDboard can be powered from any one of the eight VGA sources.
Linear Technology’s high performance battery management ICsenable long battery life and run time, while providing precision charging control, constantstatus monitoring and stringent battery protection. Our proprietary design techniques seamlesslymanage multiple INPUT sources while providing small solution footprints, faster charging and100% standalone operation. Battery and circuit protection features enable improved thermalperformance and high reliability operation.
Abstract: This application note illustrates an intermediate 8V switching power supply for an automotive radio and infotainment system.The design withstands the complete automotive INPUT voltage range (including cold crank and load dump conditions), assuring a stable8V supply for common subsystems such as a CD driver, LCDs, and a radio module in modern infotainment systems. To avoiddisturbance in the AM and FM bands, the switching power supply runs at a fixed frequency of 2MHz, enabling an ideal solution forradio systems.
