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Circuits from the Lab™ reference circuits are engineered and tested for quick and easy system integration to help solve today's analog, mixed-signal, and RF design challenges.
This true rms responding power detector uses a variable gain amplifier (VGA) and a power detector to provide a 95-dB wide detection range, making it useful for accurate measurement of signals with diverse or varying crest factors, such as those found in GSM/EDGE, CDMA, WCDMA, TD-SCDMA, and LTE receivers and transmitters. The 65-dB detection range of the ADL5902 rms detector is extended to 95 dB by the addition of the AD8368 linear-in-dB VGA.
This flexible, frequency agile, direct conversion IF-to-baseband receiver features a fixed 5-dB conversion gain to reduce the cascaded noise figure. Variable baseband gain adjusts the signal level, and a programmable low-pass filter eliminates out-of-channel blockers and noise. The filter bandwidth can be dynamically adjusted as the input signal bandwidth changes, ensuring full use of the available dynamic range of the driven ADC. The core circuit is an integrated I/Q demodulator with fractional-N PLL and VCO. With a single variable reference frequency, the PLL/VCO can provide a local oscillator (LO) between 750 MHz and 1150 MHz.
This complete high-performance resolver-to-digital (RDC) circuit accurately measures angular position and velocity in automotive, avionics, and critical industrial applications where high reliability is required over a wide temperature range. The innovative resolver rotor driver circuit has two modes of operation: high performance and low power. In high-performance mode, the system operates on a 12-V supply and can supply 6.4 V rms (18 V p-p) to the resolver. In low-power mode, the system operates on a 6-V supply and can supply 3.2 V rms (9.2 V p-p) to the resolver, while drawing less than 100 mA. Active filtering is provided in both driver and receiver to minimize the effects of quantization noise. The maximum tracking rate is 3125 rps in 10-bit mode (resolution = 21 arc min) and 156.25 rps in 16-bit mode (resolution = 19.8 arc sec).
This high-performance multichannel data acquisition circuit has been optimized for fast channel-to-channel switching with industrial signal levels. It can process 16 single-ended channels or eight differential channels, with 18-bit resolution at sampling rates up to 1.33 MSPS. A 250-kHz channel-to-channel switching rate provides 16-bit performance, making it an ideal solution for multichannel data acquisition in process control and power line monitoring applications.
This contactless, AMR (anisotropic magnetoresistive) angle measurement solution provides 1° angular accuracy over a 180° range, making it ideal for applications that require accurate, high speed, non-contact angle measurements. The full signal chain, which includes instrumentation amplifiers, buffers, and a dual channel ADC, efficiently processes the AMR sensor’s low level bridge outputs. The result is an industry leading angle measurement solution suitable for machine tool speed control, crane angle control, motor speed measurement, and other applications.
This PLL circuit uses a 13-GHz fractional-N synthesizer, wideband active loop filter, and VCO, to achieve phase settling time of less than 5 μs to within 5° for a 200-MHz frequency jump. The performance is achieved using an active loop filter with 2.4-MHz bandwidth. This wideband loop filter is enabled by the 110-MHz maximum frequency of the ADF4159’s phase-frequency detector (PFD); and the 145-MHz gain-bandwidth product of the AD8065 op amp. The AD8065 can operate on a 24 V supply voltage, allowing control of most wideband VCOs having tuning voltages from 0 V to 18 V.
This completely isolated current sensor with isolated power source is highly robust and can be mounted close to the sense resistor for accurate measurements and minimum noise pickup. The 16-MHz output data stream from a sigma-delta modulator is processed by a DSP using a SINC3 digital filter. Ideal for monitoring the ac current in solar photovoltaic (PV) converters, the circuit can handle peak ac voltages of several hundred volts and currents between a few mA and 25 A.
This completely isolated low power pH sensor signal conditioner and digitizer with automatic temperature compensation achieves 0.5% accuracy for pH between 0 and 14, with greater than 14-bits of noise-free code resolution, making it suitable for a variety of industrial applications such as chemical, food processing, water, and wastewater analysis. It supports a wide variety of pH sensors with internal resistance that can range from 1 MΩ to several GΩ. Digital signal and power isolation provides immunity to noise and transient voltages often encountered in harsh industrial environments.
This 18-bit, 5-MSPS, low-power, low-noise, high-precision, complete data-acquisition signal-chain solution dissipates only 122 mW. The reference, reference buffer, driver amplifiers, and ADC provide an optimized solution with industry-leading 99-dB SNR and −117-dB THD. Its low power and small PCB footprint make it ideal for portable applications.
This high-performance phase locked loop (PLL) uses high-speed clock buffers and low-noise LDOs to maintain low phase noise even at low reference and RF frequencies. For example, the ADF4106 PLL specifies a 20-MHz minimum reference frequency and a 500-MHz minimum RF input frequency. This frequency range can be lowered to a 10-MHz reference frequency and a 100-MHz RF input frequency using additional clock buffers.
This completely isolated 4-channel temperature measurement circuit, optimized for performance, input flexibility, robustness, and low cost, supports all types of thermocouples with cold-junction compensation and 2-, 3-, or 4-wire RTDs with resistances up to 4 kΩ. The RTD excitation current is programmable for optimum noise and linearity. RTD measurements achieve 0.1°C typical accuracy, and Type-K thermocouple measurements achieve 0.05°C typical accuracy. The circuit uses a 4-channel AD7193 24-bit sigma-delta ADC with on-chip PGA for high accuracy and low noise. Input transient and overvoltage protection are provided by low-leakage transient voltage suppressors and Schottky diodes. The SPI-compatible digital inputs and outputs are isolated to 2500 V rms, and the circuit operates on a fully isolated power supply.
This 10-MHz to 6-GHz wideband active mixer has a direct interface to a frequency synthesizer-based low phase noise local oscillator (LO). It offers an optimum solution for wideband applications that require frequency conversion to higher or lower frequencies. The two-chip circuit covers a broad LO frequency range from 35 MHz to 4400 MHz. The LO interface is simple and glueless, eliminating the need for a balun, matching network, and LO buffer. In addition, the mixer bias adjust function allows optimization of IP3, noise figure, and supply current based on the application requirements or on the size of the input signal.
This circuit offers a high linearity, low noise, wide-bandwidth vibration sensing solution that is ideal for applications, such as bearing analysis, engine monitoring, and shock detection, that require high dynamic range (±70 g to ±500 g) and flat frequency response to 22 kHz.
This professional-grade studio or live-performance microphone uses up to 32 analog MEMS microphones connected to op amps and a difference amplifier. Designed for low noise, its output is linear for acoustic inputs up to 131 dB SPL. Powered from a single 9-V battery, the ±9-V and 1.8-V power rails are generated from two voltage regulators. The ADMP411, which consists of a MEMS microphone element and an impedance-matching amplifier, has a frequency response that is flat to 28 Hz, making it ideal for full-bandwidth, wide dynamic range audio capture.
This circuit provides two, 16-bit, fully isolated, universal analog input channels suitable for programmable logic controller (PLC) and distributed control system (DCS) modules. Both channels are software programmable and support a number of voltage and current ranges and thermocouple and RTD types. The inputs are protected for dc overvoltage conditions of ±30 V. The demonstration board contains two fully isolated universal input channels: in one, the voltage, current, thermocouple, and RTD inputs all share the same terminals to minimize the number of pins required; in the other, separate terminals for voltage/current inputs and thermocouple/RTD inputs provides a lower part count and component cost.
This circuit provides a low cost solution to temperature monitoring because most of the circuit functionality is integrated into the ADuCM360 precision analog microcontroller, including dual 24-bit Σ-Δ ADCs, the ARM Cortex™-M3 processor core, and the PWM/DAC features for controlling the 4 mA-to-20 mA loop for loop voltages up to 28 V.
This 16-bit, ultra-stable, low-noise, precision, bipolar (±10 V) voltage source requires a minimum number of precision external components. It features ±0.5 LSB maximum integral nonlinearity (INL) and differential nonlinearity (DNL) with the AD5760 voltage-output DAC (B-grade). The complete system has less than 0.1-LSB p-p noise and drift measured over a 100-second interval. The circuit is ideal for medical instrumentation, test and measurement, and industrial control applications where precision low drift voltage sources are required.
This complete adjustment-free linear variable differential transformer (LVDT) signal conditioning circuit can accurately measure linear displacement (position). The LVDT is a highly reliable sensor because the magnetic core can move without friction and does not touch the inside of the tube. Therefore, LVDTs are suitable for flight control feedback systems, position feedback in servomechanisms, automated measurement in machine tools, and many other industrial and scientific electromechanical applications where long term reliability is important. This circuit uses the AD698 LVDT signal conditioner, which contains a sine wave oscillator and a power amplifier to generate the excitation signals that drive the primary side of the LVDT. The AD698 also converts the secondary output into a dc voltage. The AD8615 rail-to-rail amplifier buffers the output of the AD698 and drives a low power 12-bit successive approximation analog-to-digital converter (ADC). The system has 82-dB dynamic range and 250-Hz system bandwidth, making it ideal for precision industrial position and gauging applications.
This circuit uses the ADuCM360 precision analog microcontroller in an accurate thermocouple temperature monitoring application and controls the 4-mA to 20-mA output current. The ADuCM360 integrates two 24-bit sigma-delta (Σ-Δ) analog-to-digital converters (ADCs), two programmable current sources, a 12-bit digital-to-analog converter (DAC), and a 1.2 V internal reference, as well as an ARM Cortex-M3 core, 126 kB flash, 8 kB SRAM, and various digital peripherals, such as UART, timers, SPIs, and I2C interfaces. The ADuCM360 is connected to a type-T thermocouple and a 100-Ω platinum resistance temperature detector, which is used for cold junction compensation. The low power Cortex-M3 core converts the ADC readings to a real temperature value. The −200°C to +350°C type-T temperature range is converted to a 4-mA to 20-mA output current. The loop-powered circuit provides a complete solution for thermocouple measurements with a minimum requirement for external components.
This low-cost, high-performance sound bar system can accept an analog stereo audio signal as an input and output up to eight channels of audio with discrete processing on each channel. The circuit offers low power consumption and high efficiency without sacrificing audio quality, making it ideal for small docking stations and portable media devices. The circuit is capable of driving headphones without the need of additional components. The ADAU1761 low power, stereo audio codec with integrated SigmaDSP® digital audio processing accepts two audio channels. It is optimized for audio applications and programmed using SigmaStudio development software for ease of use and faster development. The output of the ADAU1761 can send up to eight channels of digital audio data to the output amplifiers using the serial interface. The ADAU1761 allows different audio signal processing in each channel, such as volume control, custom equalization, filtering, and spatialization effects tuned to the specific speaker configuration. The ADAU1761 processes and converts analog audio to digital format and drives the SSM2518 power amplifier. The SSM2518 is a digital input class-D audio power amplifier that can output two channels of audio with a continuous power of 2 watts each into a 4 Ω load. The channel-mapping feature of the SSM2518 allows it to select the specific channel to output among those that are available in the interface, making it ideal for surround sound applications.
This flexible current transmitter converts the differential voltage output from a pressure sensor to a 4-mA to 20-mA current. Optimized for a wide variety of bridge-based voltage or current driven pressure sensors, it utilizes only five active devices and has a total unadjusted error of less than 1%. The power supply voltage can range from 7 V to 36 V depending on the component and sensor driver configuration. The input of the circuit is protected for ESD and voltages beyond the supply rail, making it ideal for industrial applications.
This robust, flexible loop-powered current transmitter converts the differential voltage output from a pressure sensor to a 4 mA-to-20 mA current output. Optimized for a wide variety of bridge based voltage or current driven pressure sensors, the design uses only four active devices and has a total unadjusted error of less than 1%. The loop supply voltage can range from 12 V to 36 V. The input of the circuit is protected for ESD and voltages beyond the supply rail, making it ideal for industrial applications.
This quad 14-bit, 125-MSPS ADC system uses post digital summation to increase the signal-to-noise ratio (SNR) from 74 dBFS for a single ADC to 78.5 dBFS for the quad ADC with summation. Especially suitable for applications such as ultrasound and radar that require high SNR, this technique makes use of modern high-performance low-power quad pipelined ADCs. The circuit makes use of the fundamental principle that uncorrelated noise sources add on a root-sum-square (rss) basis, while signal voltages add on a linear basis.
This complete, fully isolated, analog output channel is suitable for programmable logic controllers (PLCs) and distributed control system (DCS) modules that require standard 4 mA to 20 mA HART®-compatible current outputs and unipolar or bipolar output voltage ranges. It provides a flexible building block for channel-to-channel isolated PLC/DCS output modules or any other industrial application that requires a fully isolated analog output. The circuit also includes external protection on the analog output terminals. The AD5422 16-bit digital-to-analog converter (DAC) is software configurable and provides all the necessary current and voltage outputs. The AD5700-1 HART-compliant modem, used in conjunction with the AD5422, forms a complete HART-compatible 4 mA to 20 mA solution. The AD5700-1 includes a precision internal oscillator that provides additional space savings, especially in channel-to-channel isolated applications.
This dual-channel colorimeter, which features a modulated light source transmitter and a synchronous detector receiver, measures the ratio of light absorbed by the sample and reference containers at three different wavelengths, providing an efficient solution for many chemical analysis and environmental monitoring instruments that measure concentrations and characterize materials through absorption spectroscopy.
This complete, adjustment-free, linear variable differential transformer (LVDT) signal conditioning circuit can accurately measure linear displacement (position). It uses the AD598 LVDT signal conditioner, which integrates a sine wave oscillator and a power amplifier to generate the excitation signals that drive the primary side of the LVDT. The system has 82-dB dynamic range and 250-Hz bandwidth, making it ideal for precision industrial position and gauging applications. This Circuit Note discusses basic LVDT theory and the design steps used to optimize the circuit for a chosen bandwidth.
These circuits demonstrate proven and tested electromagnetic compatibility (EMC) compliant solutions for three protection levels for popular RS-485 communication ports using the ADM3485E transceiver. Each solution was tested and characterized to ensure that the dynamic interaction between the transceiver and the protection circuit components functions correctly together to protect against the electrostatic discharge (ESD), electrical fast transients (EFT), and surge immunity specified in IEC 61000-4-2, IEC 61000-4-4, and IEC 61000-4-5, respectively. The circuits offer proven protection for RS-485 interfaces using the ADM3485E to the ESD, EFT, and surge levels often encountered in harsh environments.
This circuit is a complete implementation of the analog portion of a broadband direct conversion transmitter (analog baseband in, RF out). It supports RF frequencies from 500 MHz to 4.4 GHz using a phase-locked loop (PLL) with a broadband, integrated voltage-controlled oscillator (VCO). Harmonic filtering of the local oscillator (LO) from the PLL ensures excellent quadrature accuracy, sideband suppression, and low EVM. Low noise, low dropout regulators (LDOs) ensure that the power management scheme has no adverse impact on phase noise and EVM. This combination of components represents industry leading direct conversion transmitter performance over a frequency range of 500 MHz to 4.4 GHz.
This complete, smart, industrial loop-powered field instrument has a 4-mA to 20-mA analog output and a highway addressable remote transducer (HART®) interface. HART is a digital 2-way communication in which a 1 mA peak-to-peak frequency-shift-keyed (FSK) signal is modulated on top of the standard 4-mA to 20-mA analog current signal. This allows features such as remote calibration, fault interrogation, and transmission of process variables in applications such as temperature and pressure control.
This broadband direct-conversion transmitter (analog baseband in, RF out) supports RF frequencies from 30 MHz to 2.2 GHz using a phase-locked loop (PLL) with an on-chip broadband voltage-controlled oscillator (VCO). Unlike modulators that use a divide-by-1 local oscillator (LO) stage, harmonic filtering of the LO is not required as long as the LO inputs to the modulator are driven differentially. The ADF4351 provides differential RF outputs and is, therefore, an excellent match. This PLL-to-modulator interface is useful for all I/Q modulators and I/Q demodulators that contain a 2XLO-based phase splitter.
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