© Analog Devices Application Notes | December 04, 2020
A Low Power, Low Cost, Differential Input to a Single-Ended Output Amplifier
Question: How do I make a low cost, low power, differential input into a single-ended output amplifier?
Answer: In many applications, there are requirements of low power, high performance differential amplifiers to convert small differential signals to a readable ground referenced output signal. Input voltages at two inputs usually share a large common-mode voltage. The differential amplifier rejects the common-mode voltage and the remaining voltage is amplified and presented on the amplifier output as single-ended voltage. The rejected voltage can either be ac or dc, and this common-mode voltage is typically larger than the differential input voltage. The effectiveness of the rejection diminishes as the frequency of the common-mode voltage increases. Amplifiers within the same package have better matching, the same parasitic capacitance, and no external wiring is needed. Therefore, a high performance, high bandwidth dual amplifier performs better with frequency than discrete amplifiers. A simple solution is to use dual precision amplifiers with a resistive gain network, as shown in Figure 1. This circuit shows a simple way of converting a differential input to a single-ended output with adjustable gain. The gain of the system can be set by Equation 1: Where gain = RF/1 kΩ and (VIN1 – VIN2) is the differential input voltage Figure 1. The differential input, single-ended output amplifier. Generally, this technique provides a more stable reading when EMI or RFI is present and, therefore, it is recommended when noise is a problem. This is especially true when measuring thermocouple, strain gage, and bridge type pressure sensor inputs, since they produce very small signals in a noisy environment. This circuit can offer a performance improvement over single-ended inputs by not only measuring the difference in voltage between the positive and negative terminals of the sensor, but also providing common-mode rejection with some system gain. Furthermore, the sensor ground can be different from the analog ground. An output voltage referenced to ground is important in many applications. The accuracy of the system depends on the tolerance of the network resistors. The circuit can convert a differential input to a single-ended output with an adjustable gain. The gain of the system can be set by the ratio of RF and RG1 with the assumption that RG2 = RG1 and amplifier B has a gain of –1. For example, the ADA4807-2, a 180 MHz dual amplifier, can be built as an inverting amplifier for this application and this circuit provides lower noise. With a low quiescent current of 1000 μA per amplifier, the circuit is ideal for low power, high resolution data conversion systems. The input common mode can go beyond the supply voltages. The output is rail to rail, which makes it useful in the presence of a large common-mode signal or a large output voltage applications. For example, the data acquisition board has an ADC that accepts a single-ended input of 0 V to 5 V. However, the signal source happens to be differential voltage generated from a sensor bridge where one terminal swings positive while the other swings negative in response to pressure in the presence of common noise. Figure 2. The performance of the simple differential to single-ended amplifier. The plot in Figure 2 was taken by applying a differential input voltage and varying the gain of the circuit. The value of RF sets the gain of the system. As one can observe, the plot shows the system gain of 1, 2, and 4, with the differential input voltage of 1 V p-p at 1 kHz. The circuit is useful for measuring a small difference between two large voltages. For example, consider a solution with a simple 1% accuracy of monitoring a typical Wheatstone bridge circuit that is excited by 3 V/GND in a 3 V battery-powered system. Using 1% resistors or better will allow for the level of accuracy needed, and the circuit will reject any common mode and amplify the attenuated bridge signal by the gain that the circuit is set for. If driving an ADC, some level-shifting will need to be applied to get the output signal in the range of 0 V to 5 V. This circuit offers a combination of excellent distortion with low quiescent current. The 2 op amp solution results in lower system cost and the use of a differential amplifier yields better performance. Authors: Chau Tran [firstname.lastname@example.org] joined © Analog Devices in 1984 and works in the Integrated Amplifier Products (IAP) Group in Wilmington, MA. In 1990, he graduated with an M.S.E.E. degree from Tufts University. Chau holds more than 10 patents and has authored more than 10 technical articles. Jordyn Rombola [ email@example.com] is a product engineer in the Linear and Precision Technology (LPT) Group here at ADI. She joined Analog Devices in January 2014 after finishing her bachelor’s degree in electrical and computer engineering from Worcester Polytechnic Institute (WPI).
Intel steps up as a supplier to the automotive industry According to Intel’s new CEO, Pat Gelsinger, the company is ready to step up and start making chips for car makers to take the edge off the current shortage that has hit the automotive industry hard.
Sponsored content by TotechLong Term Storage Safe, secure storage and quality testing of sensitive components Shortage of electronic components Worldwide there is a significant shortage of electronic components, especially SMT components. The Long Term Storage of electronic components can be the solution for this problem in the future. But the requirements for long-term storage are increasing.
Fund II triples the size of TDK Ventures’ Fund I TDK Corporation's subsidiary TDK Ventures Inc. has closed its second fund, totalling USD 150 million in new capital. The new fund will primarily target early-stage, global investments in clean technology, advanced materials, industrial, robotics, energy, autonomous vehicles, electric vehicles, and healthtech segments.
MacDermid Alpha opens new die attach applications centre MacDermid Alpha Electronics Solutions officially opened a Greater China Die Attach Application Centre on April 1st, 2021. The technology and application centre will house technical service and lab personnel, equipped with die attach assembly and process equipment.
WISeKey to increase manufacturing capabilities to support demand Cybersecurity and IoT company, WISeKey, says that it is significantly investing in its supply chain transformation to better and faster serve its customers. The company is simultaneously impacted by the current semiconductor shortage situation and a tremendously growing order backlog.
Renesas resumes operations at fire damaged facility Renesas say that the N3 Building (300mm line) clean room at Naka Factory resumed operations on Friday April 9.
Sponsored content by Shenzen Kinwong ElectronicThe development trend of printed circuit board products and Kinwong's solution With the rapid development of electronic technology in recent years, printed circuit board (PCB) products are pursuing higher heat dissipation capabilities, with high voltage and high current characteristics, and are developing towards high-density interconnection technology (HDI).
Neonode to supply its tech to a major South Korean elevator OEM Neonode has received an order for and will supply touch sensor modules to Finetek, a Neonode value-added reseller, who has been selected by a major elevator OEM in South Korea to install its contactless elevator control panel solutions powered by Neonode’s technology in existing elevators in this market.
High Speed ADC Power Supply Domains Question: Why are there all these power domains for high speed ADCs?
BAE Systems receives adaptive RF contracts from DARPA BAE Systems will design mechanisms for the U.S. Defense Advanced Research Projects Agency (DARPA) that protect emerging wideband receivers from interference, enabling their use in contested and congested environments.
Swedish biometrics company expands in Europe and Asia Swedish biometrics company, Fingerprint Cards, is seeing more and more reasons to move closer to "the action". The world’s top three payment card producers are all based in continental Europe, while most of the largest smartphone OEMs are headquartered in Asia - so that's where the company's heading.
Sponsored content by Würth Elektronik eiSosFour days of concentrated electronics knowledge Würth Elektronik invites you to a virtual conference with expert presentations on EMC, thermal management, power management, connectivity, and many other circuit design topics from April 26-29, 2021 from 8 am to 6 pm CET each day.
Siemens Mobility to triple R&D headcount in Hungary Siemens Mobility is set to create 120 new R&D related jobs at its Budapest, Hungary location as the company moves moves forward in its efforts to "digitalise track-based transport modes".
AMD and Xilinx stockholders approve proposed acquisition The stockholders of both companies voted to approve their respective proposals relating to the pending acquisition of Xilinx by AMD.
Renesas to shift production from fire-hit Naka fab The Japanese semiconductor manufacturer is reportedly set to shift some production from its fire damaged Naka fab to a facility in the southwestern prefecture of Ehime.
Netlist and SK hynix reach patent and technology agreement Netlist and SK hynix have reached an agreement for a patent cross license covering memory technologies of both companies and an agreement for the supply of SK hynix products and technical cooperation on Netlist's CXL HybriDIMM technology.
Sponsored content by Rochester ElectronicsManaging Semiconductor Component Obsolescence Rochester Electronics discusses why it is imperative to purchase components from fully authorized sources who are AS6496 compliant.
For the many professionals tasked with maintaining products and systems with mission-critical components that have gone into obsolescence, building a reliable supply chain for these parts is crucial.
13% increase to lift total semi shipments to a new record high Total semiconductor unit shipments, which include integrated circuits as well as optoelectronics, sensor/actuator, and discrete (O-S-D) devices, are forecast to rise 13% in 2021, to 1,135.3 billion (1.1353 trillion) units to set a new all-time annual record.
ROHM Semiconductor Europe appoints new President As of April 1st, 2021, Wolfram Harnack has taken the helm as ROHM Semiconductor Europe's new President. Former President, Toshimitsu Suzuki, will lead the European Sales Division as General Manager from the company's headquarters in Japan.
SK hynix negotiates supply deal with Bosch The South Korean company is reportedly in talks with Germany’s Robert Bosch Gmbh regarding a long-term supply contract.
Camtek receives orders worth more than $20 million The developer and manufacturer of inspection and metrology equipment for the semiconductor industry, says that in recent weeks it has received orders for inspection and metrology systems totaling over USD 20 million.
u‑blox acquires full ownership in Sapcorda JV Wireless and positioning technology specialist, u-blox, says that it has acquired full ownership of Sapcorda Services GmbH, a joint venture formed by u‑blox, Bosch, Geo++, and Mitsubishi Electric.
Murata spins off plant – establishes new company Murata Manufacturing says it will spin off its Kanazawa Murata Manufacturing Sendai plant and establish a new group company with the name of Sendai Murata Manufacturing, on July 1, 2021.
Problem solver: Multiplying digital-to-analog converter Question: How could a multiplying DAC be used other than as a DAC?
UCT completes acquisition of Ham-Let Ultra Clean Holdings (UCT) has completed the acquisition of Ham-Let (Israel-Canada) Ltd. for approximately USD 351 million. The acquisition expands UCT's addressable market in semiconductors
Axcelis ships multiple systems to CMOS image sensor manufacturers Axcelis Technologies says that it has shipped multiple Purion VXE high energy systems to CMOS image sensor manufacturers. While the CMOS image sensor manufacturers remain unnamed, Axcelis describes them as leading.
Zeiss opens US high-tech centre in the Bay Area Optics and optoelectronics technology company Zeiss has completed the construction of its new R&D, production, sales and customer service site in the San Francisco Bay Area.
Shenmao sets up testing lab in Taiwan - Cheetah Inspection Shenmao has established an independent testing laboratory in Taiwan called Cheetah Inspection Inc. The ISO/IEC 17025 approved testing laboratory is located in Hsinchu.
TSMC to invest $100 billion to increase capacity In the midst of a global semiconductor shortage, the manufacturing giant announces that it is planning to invest USD 100 billion over the course of three years.Load more news