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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 complete linear variable differential transformer (LVDT) signal conditioning circuit can accurately measure linear position or displacement from a mechanical reference. Synchronous demodulation in the analog domain extracts the position information and provides immunity to external noise. A 24-bit, Σ-Δ analog-to-digital converter (ADC) digitizes the position output for high accuracy. LVDTs utilize electromagnetic coupling between the movable core and the coil assembly. Contactless, frictionless operation is a primary reason for their use in aerospace, process controls, robotics, nuclear, chemical plants, hydraulics, power turbines, and other applications where operating environments can be hostile and long life and high reliability are required. The entire circuit, including the LVDT excitation signal, consumes only 10 mW. The excitation frequency and output data rates are SPI programmable. The bandwidth can be traded for dynamic range. Supporting bandwidths of over 1 kHz, the circuit has 100-dB dynamic range at 20 Hz, making it ideal for precision industrial position and gauging applications.
This compact two-chip circuit provides a contactless anisotropic magnetoresistive (AMR) measurement solution ideal for either angle or linear position measurements. The two-chip system is capable of providing better than 0.2° angular accuracy over 180°, and linear accuracy of 2 mil (0.002 inch) over a 0.5 inch range, depending on the size of the magnet used. The circuit is ideal for applications where high speed, accurate, noncontact angle and length measurements are critical, such as machine tool speed control, crane angle control, brushless dc motors, and other industrial or automotive applications.
This RF transmitter utilizes the AD9142A TxDAC, ADRF6720 wideband I/Q modulator with integrated phase-locked loop (PLL) and voltage controlled oscillator (VCO), and ADL5320 ¼-W driver amplifier. Signal biasing and scaling in the DAC-to-modulator interface circuit is controlled by four ground referenced resistors and two shunt resistors, respectively. The input and output matching on the ADL5320 driver amplifier is implemented using shunt capacitors at the input and the output.
This circuit isolates a peripheral device that already implements a USB interface. It is not possible to make a fully compliant bus-powered cable because there are no 100% efficient power converters to transfer the bus voltage across the barrier. In addition, the quiescent current of the converter does not comply with the standby current requirements of the USB standard. This is all in addition to the speed detection limitations of the ADuM4160. What can be achieved is a fixed speed or switch-controlled speed cable that can supply a modest power to the downstream peripheral. This custom application is not completely compliant with the USB standard.
This complete, fully isolated, highly flexible, four-channel analog input system is suitable for programmable logic controller (PLC) and distributed control system (DCS) applications that require multiple voltage inputs and HART-compatible 4-mA to 20-mA current inputs. The analog input circuit, designed for group isolated industrial analog inputs, can support voltage and current input ranges including ±5 V, ±10 V, 0 V to 5 V, 0 V to 10 V, 4 mA to 20 mA, and 0 mA to 20 mA. The circuit is powered from a standard 24-V bus supply and generates an isolated 5-V system supply voltage.
This battery powered circuit uses an ADuCRF101 precision analog microcontroller with ARM Cortex-M3 processor and ISM-band RF transceiver to transmit wind speed and wind direction from a passive anemometer. The on-chip 12-bit analog-to-digital converter (ADC) and the wake-up timers acquire the wind direction and speed, respectively. In low-power hibernation mode, the ADuCRF101 draws 1.8 μA of supply current, resulting in long battery life, which is an important feature in wireless remote sensing applications. A single CR2032 Li-Ion battery can last 1 year to 2 years when operated in this mode.
This isolated flyback power supply uses a linear isolated error amplifier to supply the feedback signal from the secondary side to the primary side. Unlike optocoupler-based solutions, which have a nonlinear transfer function that changes over time and temperature, the linear transfer function of the isolated amplifier is stable and minimizes offset and gain errors when transferring the feedback signal across the isolation barrier. The entire circuit operates from 5 V to 24 V, allowing it to be used with standard industrial and automotive power supplies. The output capability of the circuit is up to 1 A with a 5-V input and 5-V output configuration. This solution can be adapted for applications where higher dc input voltages are used to create lower voltage isolated supplies with good efficiency and a small form factor. Examples include 10 W to 20 W telecommunication and server power supplies, where power efficiency and printed circuit board density are important and –48-V supplies are common.
This robust, completely isolated industrial 4-channel data-acquisition system provides 16-bit noise-free code resolution, less than 15 ppm channel-to-channel crosstalk, and an up to 42-kSPS channel switching rate. The circuit acquires and digitizes industrial signal levels of ±5 V, ±10 V, 0 V to 10 V, and 0 mA to 20 mA. The input buffers provide overvoltage protection, thereby eliminating the leakage errors associated with conventional Schottky diode protection circuits. Applications for the circuit include process control (PLC/DCS modules), battery testing, scientific multichannel instrumentation, and chromatography.
This accurate 40-GHz, microwave power meter with 45-dB range requires only two components. The RF detector uses an innovative detector cell composed of Schottky diodes followed by an analog linearization circuit. A low-power, 12-bit, 1-MSPS analog-to-digital converter (ADC) provides a digital output on a serial peripheral interface (SPI) port. After a simple calibration routine is run at the RF frequency of interest, the user can operate the system in measurement mode. The evaluation software displays the calibrated RF input power in units of dBm.
This frequency selective, radio frequency (RF) detector offers a 90-dB detection range from 35 MHz to 4.4 GHz. Unlike a standalone detector that does not discriminate between signals in the frequency spectrum, this circuit can focus on a narrow band of frequencies, enhancing performance over the specified range. The rms responding circuit is stable vs. temperature and frequency, making it attractive for applications that require precise frequency control, selective RF power measurement, and strong immunity to unwanted blockers.
This complete, low-power signal conditioner for bridge-type sensors includes a temperature compensation channel. Ideal for a variety of industrial pressure sensors and load cells that operate with drive voltages of between 5 V and 15 V, this circuit can process full-scale signals from approximately10 mV to 1 V using the internal programmable gain amplifier (PGA) of the 24-bit, sigma-delta (Σ-Δ) ADC. The entire circuit uses only three ICs and requires only 1 mA, excluding the bridge current. A ratiometric technique ensures accuracy and stability without a voltage reference.
This single supply, low noise, portable gas detector, uses an Alphasense CO-AX electrochemical sensor to detect carbon monoxide. Electrochemical sensors offer several advantages for instruments that detect or measure the concentration of many toxic gases. Most sensors are gas specific and have usable resolutions under one part per million (ppm) of gas concentration. The circuit uses the ADA4528-2 dual auto-zero amplifier, which has a 2.5 µV maximum offset voltage at room temperature and an industry leading 5.6 µV/√Hz voltage noise density, and the AD5270-20 programmable rheostat, allowing for rapid prototyping of different gas sensor systems without changing the bill of materials. The ADR3412 precision, low noise, micropower reference establishes the 1.2 V common-mode, pseudo ground reference voltage with 0.1% accuracy and 8 ppm/°C drift.
This circuit combines the AD5755-1 four-channel voltage and current output DAC with dynamic power control and the AD5700-1 HART modem, to impement a completely isolated multiplexed HART analog output solution. Power can be provided either from the transformer isolated power circuit provided on the board or from external power supplies connected to terminal blocks. This circuit is suitable for use in programmable logic controllers (PLCs) and distributed control system (DCS) modules that require multiple HART-compatible 4 mA to 20 mA current outputs, along with unipolar or bipolar voltage outputs. External transient protection circuitry is also included, which is important for applications located in harsh industrial environments.
This 12-bit, 1-MSPS data-acquisition system uses only two active devices. The system processes charge input signals from piezoelectric sensors using a single 3.3-V supply and has a total error of less than 0.25% FSR after calibration over a ±10°C temperature range, making it ideal for a wide variety of laboratory and industrial measurements. The circuit’s small footprint makes this combination an industry-leading solution for data-acquisition systems where accuracy, speed, cost, and size play a critical role.
This self-contained distance sensor utilizes an ultrasonic transmitter and sensitive analog receiver in conjunction with a precision analog microcontroller to provide distance measurements. Unlike complicated PLL-based receivers, the sensor uses a sensitive window comparator circuit, thereby minimizing real estate and cost. The approximate range is from 50 cm to 10 m with a resolution of about 2 cm. Temperature compensation is provided by the integrated temperature sensor and ADC contained in the microcontroller. For sensing the levels of thick liquids or foamy water, the ultrasonic level sensor is a better choice than capacitance, reed, or float sensors. In very dusty or corrosive environments, the ultrasonic sensor is the sensor of choice.
This 75-MHz low-power (25 mW total) direct digital synthesis (DDS) waveform generator includes an output buffer and anti-imaging filter to provide improved spectral performance, making it suitable for frequency generation or clocking applications requiring sine wave, triangular wave, and square outputs up to 18 MHz. As sampled data devices, low-power DDS devices must be followed by a suitable anti-imaging filter to remove spectral images, but their maximum current output is approximately 4 mA into a recommended 200-Ω load, so an op amp buffer at the DDS output is required to provide a low-impedance drive source for a high-quality 50-Ω filter. The combination of the DDS, output buffer, and seventh-order elliptic low pass filter provides high-quality spectral performance.
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