Abstract: IC switches and multiplexers are proliferating, thanks to near-continual progress in lowering the supply Voltage,incorporating fault-protected inputs, clamping the output Voltage, and reducing the switch resistances. The latest of these advancesis the inclusion of precision resistors to allow two-point calibration of gain and offset in precision data-acquisition systems.
Abstract: This tutorial discusses methods for digitally adjusting the output Voltage of a DC-DC converter. The digital adjustmentmethods are with a digital-to-analog converter (DAC), a trim pot (digital potentiometer), and PWM output of a microprocessor.Each method is assessed and several DACs and digital potentiometers presented.
The purpose of this application note is to show an example of how a digital potentiometer can be used in thefeedback loop of a step-up DC-DC converter to provide calibration and/or adjustment of the output Voltage.The example circuit uses a MAX5025 step-up DC-DC converter (capable of generating up to 36V,120mWmax) in conjunction with a DS1845, 256 position, NV digital potentiometer. For this example, the desiredoutput Voltage is 32V, which is generated from an input supply of 5V. The output Voltage can be adjusted in35mV increments (near 32V) and span a range wide enough to account for resistance, potentiometer and DCDCconverter tolerances (27.6V to 36.7V).
The LT®6552 is a specialized dual-differencing 75MHzoperational amplifier ideal for rejecting common modenoise as a video line receiver. The input pairs are designedto operate with equal but opposite large-signal differencesand provide exceptional high frequency commonmode rejection (CMRR of 65dB at 10MHz), therebyforming an extremely versatile gain block structure thatminimizes component count in most situations. The dualinput pairs are free to take on independent common modelevels, while the two Voltage differentials are summedinternally to form a net input signal.
Abstract: Transimpedance amplifiers (TIAs) are widely used to translate the current output of sensors like photodiode-to-Voltagesignals, since several circuits and instruments can only accept Voltage input. An operational amplifier with a feedback resistor fromoutput to the inverting input is the most straightforward implementation of such a TIA. However, even this simple TIA circuit requirescareful trade-offs among noise gain, offset Voltage, bandwidth, and stability. Clearly stability in a TIA is essential for good, reliableperformance. This application note explains the empirical calculations for assessing stability and then shows how to fine-tune theselection of the feedback phase-compensation capacitor.
Who has never experienced oscillations issues when using an operational amplifier? Opampsare often used in a simple Voltage follower configuration. However, this is not the bestconfiguration in terms of capacitive loading and potential risk of oscillations.Capacitive loads have a big impact on the stability of operational amplifier-basedapplications. Several compensation methods exist to stabilize a standard op-amp. Thisapplication note describes the most common ones, which can be used in most cases.The general theory of each compensation method is explained, and based on this, specific
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.
Digital-to-analog converters (DACs) are prevalent inindustrial control and automated test applications.General-purpose automated test equipment often requiresmany channels of precisely controlled Voltagesthat span several Voltage ranges. The LTC2704 is ahighly integrated 16-bit, 4-channel DAC for high-endapplications. It has a wide range of features designed toincrease performance and simplify design.
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.
Recent advances in low Voltage silicon germaniumand BiCMOS processes have allowed the design andproduction of very high speed amplifi ers. Because theprocesses are low Voltage, most of the amplifi er designshave incorporated differential inputs and outputs to regainand maximize total output signal swing. Since many lowVoltageapplications are single-ended, the questions arise,“How can I use a differential I/O amplifi er in a single-endedapplication?” and “What are the implications of suchuse?” This Design Note addresses some of the practicalimplications and demonstrates specifi c single-endedapplications using the 3GHz gain-bandwidth LTC6406differential I/O amplifi er.
