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This 11-page Application Note describes a reference design using the ADF7241/ADF7242 highly integrated, low power, high performance transceiver and the SE2431L fully integrated RF front-end. The ADF7241 and ADF7242, which operate in the global 2.4-GHz ISM band, provides flexibility, robustness, ease of use, and low current consumption. They support the IEEE 802.15.4-2006 2.4‑GHz PHY requirements. The ADF7242 also supports proprietary GFSK/FSK/GMSK/MSK modulation schemes in both packet and data streaming modes. The Skyworks SE2431L, designed for 2.4 GHz applications, provides ease of use and maximum flexibility, with fully matched 50 Ω input and output, integrated interstage matching, harmonic filter, and digital controls that are compatible with 1.6 V to 3.6 V CMOS levels.
Heterodyne radios, such as the ADF7021 family of transceivers, use a mixer to down convert received RF signals to an intermediate frequency (IF). The output of the mixer contains the wanted frequency component along with an unwanted component at the image frequency. Unwanted signals present at the image frequency can degrade receiver sensitivity, resulting in loss of signal on the wanted channel. In theory, transceivers employing an I/Q receive architecture can be configured to infinitely reject the image frequency, assuming that the gain balance and the phase orthogonality of the mixer quadrature paths are perfectly aligned. In practice, some imbalance exists due to imperfections in the mixer. The image calibration process adjusts the gain and phase of the mixer via a digital control register until the quadrature signals are optimally balanced, providing maximum image rejection. This 11-page Application Note provides information on the mechanism that generates the image frequency and describes how image calibration can be implemented on the ADF7021, ADF7021-N, and ADF7021-V.
This circuit provides a low cost, low power video multiplexer using the ADA4853-2 dual high speed amplifier, allowing a fourth video input to an ADV7180 3-channel video decoder, saving cost and board space.
This circuit uses the ADL5534 IF amplifier to provide a dual IF gain block for the AD9640 14-bit, 150 MSPS dual ADC. The ADL5534 high linearity, dual amplifier with fixed 20 dB gain can be adapted for use as a driver for a high performance IF sampling ADC. The ADL5534 provides a simple approach to interfacing the RFIN signal level of 200 mV p-p to the 2 V p-p full scale of the high speed ADC. The low noise (2.5 dB NF at 70 MHz) and low distortion (IP3 of 40 dBm at 70 MHz) of the ADL5534 ensure that the ADC performance is not compromised.
This circuit provides an ultralow distortion driver circuit for the AD7991 12-bit, 4-channel, analog-to-digital converter (ADC) that is designed to achieve optimum ac and dc performance. It uses the ultralow distortion, ultralow noise AD8599 dual-supply op amp and ultrahigh precision AD780 band gap voltage reference to ensure that the maximum AD7991 performance is achieved by providing a low impedance driver with adequate settling time and a highly accurate reference voltage.
This circuit provides a compact, low-cost, low-voltage, inverting variable-gain amplifier using the AD5270/AD5272 digital rheostat in conjunction with the AD8615 operational amplifier. The small size and low cost of the AD5270/AD5272 and AD8615 present an industry leading solution to a common analog signal processing circuit. The circuit offers 1024 different gains, controllable through an SPI (AD5270) or I2C-compatible (AD5272) serial digital interface. The ±1% resistor tolerance of the AD5270/AD5272 provides low gain error over the full resistor range. The circuit supports rail-to-rail inputs and outputs for both single-supply operation at +5 V and dual-supply operation at ±2.5 V and is capable of delivering up to ±150 mA output current. In addition, the AD5270 and AD5272 have an internal 50-times programmable memory that allows a customized gain setting at power-up. Well suited for signal conditioning, the circuit provides high accuracy, low noise, and low THD.
This circuit provides a compact, low-cost, low-voltage, noninverting variable-gain amplifier using the AD5270/AD5272 digital rheostat in conjunction with the AD8615 operational amplifier. The small size and low cost of the AD5270/AD5272 and AD8615 present an industry leading solution to a common analog signal processing circuit. The circuit offers 1024 different gains, controllable through an SPI (AD5270) or I2C-compatible (AD5272) serial digital interface. The ±1% resistor tolerance of the AD5270/AD5272 provides low gain error over the full resistor range. The circuit supports rail-to-rail inputs and outputs for both single-supply operation at +5 V and dual-supply operation at ±2.5 V and is capable of delivering up to ±150 mA output current. In addition, the AD5270 and AD5272 have an internal 50-times programmable memory that allows a customized gain setting at power-up. Well suited for signal conditioning, the circuit provides high accuracy, low noise, and low THD.
This circuit provides a programmable bidirectional Howland current source using the AD5292 digital potentiometer in conjunction with the quad ADA4091-4 op amp and the ADR512 voltage reference. This circuit offers 10-bit resolution over a ±18.4-mA output current range. The AD5292 is programmable over an SPI-compatible serial interface. The ±1% resistor tolerance of the AD5292 allows it to be placed in series with external divider resistors to reduce the maximum output current without the need to match the resistors in the circuit. Reducing the IOUT range serves to increase the sensitivity of the output current. The AD5292 has an internal 20-times programmable memory that allows a customized IOUT at power-up. Well suited for digital calibration applications, the circuit provides an accurate, low-noise, low-drift output voltage.
This circuit provides a low-cost, programmable, high-voltage source with boosted output current using the AD5292 digital potentiometer in conjunction with the OP184 operational amplifier. The BSS138 PMOS transistor and Si2307CDS NMOS transistor provide current drive capability up to 2.5 A. The circuit offers 1024 different voltage settings, controllable through an SPI-compatible digital interface. This circuit offers 10-bit resolution over a 0-V to 30-V output voltage range and is capable of delivering up to 2.5 A output current. The ±1% resistor tolerance of the AD5292, in conjunction with an external resistor, increases the accuracy of the circuit by providing 10-bit resolution over a reduced output voltage range. This, in effect, creates a vernier DAC, which offers higher resolution over the reduced range. In addition, the AD5292 has an internal 20-times programmable memory that allows a customized VOUT at power-up. Well suited for power applications, the circuit provides an accurate, low-noise, low-drift output voltage and high current capability.
This circuit provides a low-cost, high-voltage, variable-gain inverting amplifier using the AD5292 digital potentiometer in conjunction with the OP184 operational amplifier. The circuit offers 1024 different gains, controllable through an SPI-compatible serial digital interface. The ±1% resistor tolerance performance of the AD5292 provides low gain error over the full resistor range. The circuit supports rail-to-rail inputs and output for 30-V single-supply operation and ±15-V dual supply operation; and is capable of delivering up to ±6.5 mA output current. In addition, the AD5292 has an internal 20-times programmable memory that allows a customized gain setting at power-up. Well suited for signal conditioning applications, the circuit provides high accuracy, low noise, and low THD.
This circuit provides high-frequency sampling using the ADL5562 high-performance, low-noise, ultralow-distortion, high-linearity differential amplifier with pin-programmable gain, plus a high-speed ADC. Optimized for driving high-frequency IF-sampling ADCs, such as the AD9445, AD9246, or AD6655, the ADL5562 provides exceptional SFDR beyond 100 MSPS at its maximum gain.
Circuits from the Lab
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 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 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 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 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.
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 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 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 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.
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.
Whether an IQ modulator is used in a direct conversion application or as an upconverter to a first intermediate frequency (IF), some gain is generally applied directly after the IQ modulator. This circuit note describes how to choose an appropriate driver amplifier to provide the first stage of gain at the output of an IQ modulator. This circuit uses the ADL5375 IQ modulator and the ADL5320 driver amplifier, which are well matched from a system performance level. Because these devices are well matched in terms of their dynamic ranges, a simple direct connection between the IQ modulator and the RF driver amplifier is recommended without any need for attenuation between the devices.
Single-supply, low-power, precision quad FET-input Buffer
The AD8244 precision, low-power, quad FET-input buffer isolates very large source impedances from the rest of the signal chain. With 2 pA max bias current and 10 TΩ input impedance, it introduces minimal error, even with MΩ source impedances. Its unique pinout physically separates the high impedance inputs from the supplies and outputs, simplifying guarding, reducing board space, and improving performance. Close channel-to-channel matching minimizes errors in differential signal chains; and its low noise, wide supply range, and high precision make it flexible enough to provide high performance anywhere a unity-gain buffer is needed, even with low source resistance. Operating with 3-V to 36-V or ±1.5-V to ±18-V supplies, the AD8244 draws 180 μA per amplifier. Available in a 10-lead MSOP package, it is specified from –40°C to +85°C and priced from $1.81 in 1000s.
Quad high-precision Op Amp features low offset, wide bandwidth, and low noise
The ADA4077-4 quad operational amplifier features 50-µV max offset, 0.55-µV/°C max drift, 1-nA max input bias current, 3.9-MHz bandwidth, 1.2-V/µs slew rate, 7-nV/√Hz noise, and outputs that are stable with capacitive loads to beyond 1000 pF with no external compensation. This combination of specifications makes the amplifier ideal for sensor signal conditioning, process control front ends, portable instrumentation, and precision filters. Operating on a ±2.5-V to ±15-V supply, the ADA4077-4 draws 400 μA per amplifier. Specified from –40°C to +125°C—with MSL1 rating for the most demanding operating environments—it is available in 14-lead SOIC and TSSOP packages and is priced at $2.90 in 1000s.
30-MHz to 4.5-GHz RF Detector has 45-dB dynamic range
The ADL5506 complete, low-cost RF detector provides a 45-dB dynamic range over the 30-MHz to 4.5-GHz frequency range. Its high sensitivity allows measurement of low power levels, thus reducing the amount of power that needs to be coupled to the detector. The output, proportional to the logarithm of the input power level, is scaled to 18 mV/dB at 900 MHz, increasing from 0.14 V to 1 V as the input signal increases from 1.25 mV rms (−45 dBm) to 224 mV rms (0 dBm). For convenience, the signal is internally ac-coupled, using a 5-pF capacitor and a broadband 50-Ω match. This high-pass coupling determines the lowest operating frequency and allows the source to be dc grounded. Intended for use in a wide variety of wireless terminal devices, the detector provides a wide dynamic range, high accuracy, and excellent temperature stability. Operating with a single 2.5-V to 5.5-V supply, the ADL5506 consumes 3.8 mA when enabled and 1 µA when disabled. Available in a 6-ball WLCSP package, it is specified from –40°C to +85°C and priced at $1.27 in 1000s.
200-MHz to 6-GHz RMS Power Detector has 35-dB dynamic range
The ADL5903 TruPwr™ rms-responding power detector provides a 35-dB dynamic range over the 200-MHz to 6-GHz frequency range. It can determine the true power of a high-frequency signal with a complex modulation envelope, including large crest factor signals such as GSM, CDMA, W-CDMA, TD-SCDMA, and LTE modulated signals. Its single-ended input is matched to 50-Ω source. The output, proportional to the logarithm of the rms value of the input, is scaled to 35.5 mV/dB at 900 MHz. The ripple-free transfer function is extremely stable over temperature. Operating with a single 3.0-V to 5.25-V supply, the ADL5903 consumes 3 mA when enabled and 100 µA when disabled. Available in an 8-lead LFCSP package, it is specified from –55°C to +125°C and priced at $2.35 in 1000s.
AD8418 high-voltage, high-resolution
current-sense amplifier measures bidirectional currents across a shunt
resistor in a variety of applications, including motor control, battery
management, and solenoid control. Its buffered output directly interfaces
with most ADCs. It features 100-dB common-mode rejection from −2 V to +70 V,
a gain of 20, and ±0.15% max gain error over temperature. Its zero-drift
core achieves ±200 μV offset, with 0.1-μV/°C offset drift over temperature
and common-mode range. Fully qualified for automotive applications, it
includes EMI filters and patented circuitry that ensures output accuracy
with pulse-width modulated common-mode voltages. Operating with a 2.7-V to
5.5-V supply, the AD8418 draws 2.6 mA. Specified from
RF Agile Transceiver
The AD9361 high-performance, highly integrated RF agile transceiver offers programmability and wideband capability that make it ideal for a broad range of transceiver applications. The device combines an RF front end with a flexible mixed-signal baseband section and integrated frequency synthesizers, simplifying design-in by providing a configurable digital interface to a processor. Operating in the 70 MHz to 6.0 GHz range, with channel bandwidths from 200 kHz to 56 MHz, the transceiver supports most licensed and unlicensed bands. Available in a 10-mm × 10-mm, 144-ball CSP_BGA package, the AD9361 is priced at $175.00 in 1000s.
High-voltage precision Operational Amplifier
ADA4700-1 high-voltage, precision operational
amplifier specifies 200-µV offset, 30-mA output current drive, 3.5-MHz
bandwidth, 20-V/µs slew rate, rail-to-rail operation, and unity-gain
stability, making it ideal for applications requiring both dc precision and
ac performance, including high-voltage test equipment, instrumentation,
regulators, power amplifiers, power supply control and protection, and
transducer buffers. It is particularly well suited for high-intensity LED
testing applications, where it provides high-accuracy voltage and current
feedback. Operating with a ±4.5-V to ±55-V supply, it draws 1.7 mA.
Available in an
Rob Reeder, Analog Fundamentals: Amplifiers, EDN, 2013-10-06
Sandro Herrera, Measure Frequency Response on Fully Differential Amplifiers Using Complex Algebra, Design News, 2013-10-01
George Alexandrov and Nathan Carter, Some Tips on Making a FETching Discrete Amplifier, Analog Dialogue, 2013-10-01
Rob Reeder, Analog Fundamentals: High-Speed PCB Design, EDN, 2013-09-17
John Ardizzoni, Efficiently Design An Op-Amp Summer Circuit, Electronic Design, 2013-08-26
Charly El-Khoury, Amplifier Disable Function Eliminates Need for Multiplexers in Multichannel Applications, Analog Dialogue, 2013-08-04
John Ardizzoni, How to Choose an Op Amp, CQ, 2013-08-01
Jonathan Pearson, Compensating Current Feedback Amplifiers in Photocurrent Applications, Analog Dialogue, 2013-07-02
Alan Walsh, Voltage Reference Design for Precision Successive-Approximation ADCs, Analog Dialogue, 2013-06-03
James Bryant, Multipliers vs. Modulators, Analog Dialogue, 2013-06-03
John Ardizzoni, Crystal Radio Sets and Op Amps, Analog Dialogue, 2013-06-03
Luis Orozco, Programmable-Gain Transimpedance Amplifiers Maximize Dynamic Range in Spectroscopy Systems, Analog Dialogue, 2013-05-01
David Buchanan, Input Magic, Analog Dialogue, 2013-05-01
Umesh Jayamohan, Understanding How Amplifier Noise Contributes to Total Noise in ADC Signal Chains, TechOnline India, 2013-04-30
David Guo, Choose Resistors to Minimize Errors in Grounded-Load Current Source, Analog Dialogue, 2013-04-01
James Bryant, Multipliers or Modulators, Analog Dialogue, 2013-04-01
John Ardizzoni, Noise Gain vs. Signal Gain, Analog Dialogue, 2013-03-06
Ryan Fletcher and Scott Wayne, Analog Devices' Engineering University--Why YOU Should Attend, Analog Dialogue, 2013-03-06
Ashraf Elghamrawi, High Performance Driver Amplifiers, Microwave Journal, 2013-02-14
Chau Tran, Marco Ablao, and Sherwin Gatchalian, Differential input to differential output amplifiers equal high temp solution, EE Times, 2013-02-06
Umesh Jayamohan, Understand How Amplifier Noise Contributes to Total Noise in ADC Signal Chains, Analog Dialogue, 2013-02-04
Chau Tran, Current transmitter operates at extremely high temperatures, EE Times, 2013-01-23
David Karpaty, Modeling Amplifiers as Analog Filters Increases SPICE Simulation Speed, Analog Dialogue, 2013-01-02
Mark Champion and Moshe Gerstenhaber, Complete, low-cost, software programmable ohmmeter measures micro-ohms, EDN, 2012-12-06
Alan Walsh, Front-End Amplifier and RC Filter Design for a Precision SAR Analog-to-Digital Converter, Analog Dialogue, 2012-12-03
Charly El-Khoury, Compensating Amplifiers That Are Stable at Gain ≥ 10 to Operate at Lower Gains, Analog Dialogue, 2012-12-03
Sandro Herrera and Moshe Gerstenhaber, Single-ended-to-differential converter has resistor-programmable gain, EDN, 2012-11-18
Reza Moghimi, Conditioning techniques for real-world sensors, EDN, 2012-11-15
Chau Tran and David Karpaty, Simple circuit measures RMS value of AC power line, EE Times, 2012-11-08
Introduction to Analog RMS-to-DC Technology: Converters and Applications – This webinar provides users with a better understanding of the underlying theory of rms, and how rms-to-dc converters work.
The Fundamentals of Voltage References and Current Sensing - This webcast will discuss voltage references and how they are used in circuit design. It will also cover and compare reference designs, specifications, reference alternatives, and application ideas such as negative references, then present how currents are handled, measured, and generated in system design.
Precision basics: How not to be surprised by unexpected error sources - This webcast, co-sponsored by Avnet EM, presents error sources of a few fundamental front end signal conditioning blocks and provides hints for better practices that will save money and speed development time.
Fundamentals of Frequency Synthesis, Part 2: Direct Digital Synthesis (DDS) – This concludes our two-part series on frequency synthesis with an introduction to direct digital synthesis. We will give a basic review of how a direct digital synthesis system works, touching on the inner workings of the DDS engine at a relatively high level. We will also discuss the tradeoffs between PLL and DDS technology as a base choice for frequency synthesis needs.
Fundamentals of Frequency Synthesis, Part 1: Phase Locked Loops – The first of a two-part series on frequency synthesis, with an introduction to phase locked loops (PLLs). This webcast looks at the need for frequency generation; techniques from the past, present, and future; how to assess the performance of a frequency synthesizer; and real world applications. Particular attention will be focused on phase locked loops as frequency synthesizers.
Fundamentals of the RF Transmission and Reception of Digital Signals - Digital Modulation is an important topic for RF designers because most modern day transceivers transmit and receive digitally modulated data. In this webcast, part of ADI's continuing FUNDAMENTALS OF DESIGN series we will introduce you to the challenges—and solutions—for digital modulation. This webcast is a great way for beginners to get introduced to this vital communications standard or for veteran RF designers learn what's new in the field.
Fundamentals of Designing with Semiconductors: Beyond the Op Amp - This webcast, the third of our 12-part series on the Fundamentals of Designing with Semiconductors for Signal-Processing Applications, premieres March 9. It looks at Difference Amps, Instrumentation Amps, Log Amps, and other important amplifiers, and explains when to use each and how to select them for maximum circuit performance.
Fundamentals of Designing with Semiconductors for Signal Processing
Applications: The Op Amp -- In this, the
second webcast of our
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