Fig.2 - In the loop compensation schematic


For designers working on these applications, it is crucial to consider any errors caused by the op amp. These errors should be targeted to be less than one Least Significant Bit (LSB) of the ADC to ensure accurate and reliable conversion. Signal conditioning: In the realm of signal conditioning, where more intricate circuits are involved, it becomes paramount for designers to consider a range of parameters to ensure optimal functionality and performance. Designers must evaluate the impact of each parameter on the overall functionality and performance of the circuit. This involves an integrated approach, considering factors like supply voltage range, quiescent current consumption, and other op amp specifications to meet the specific requirements of the application. The voltage, current to voltage conversion and signal buffering considerations all come into play and are crucial in shaping the effectiveness of signal conditioning circuits.


STMicroelectronics recognise it is not easy to select the correct op amp for an application, so they have developed a free application for Android and iOS environments which helps designers select the most suitable device, it includes a cross reference and interactive schematics


with component value calculation tools. Scan the QR code to download the free tool.


Fig.3 - Snubber network compensation schematic Out-of-the-loop compensation: A resistor (ROL (CIL ) is added


to the circuit out of the feedback loop as shown in Fig.1. In the loop compensation: A resistor (RIL


) and a capacitor


) and added in the feedback loop as shown in Fig.2. This configuration also offers the advantage of low output impedance.


) is connected between the output and ground as shown in Fig.3. It stabilizes op amps driving capacitive loads and is particularly recommended for lower voltage applications, where the full output swing is needed.


(RSN


Snubber network compensation: Here a RC series circuit & CSN


Typical application considerations Each application has different key requirements for op amp performance. Generally, we can subdivide applications into different categories as follows. Voltage amplification: When it comes to amplifying low-voltage signals with precision, selecting high-quality op amps becomes crucial as the input offset voltage directly impacts the accuracy of the measurement. ST offers precision op amp solutions that cater to this requirement, including zero-drift amplifiers and amplifiers with low offset drift over temperature. Op amps such as the TSU111 are an excellent choice for various sensors, such as gas, temperature, pressure, and position sensors.


For current sensing applications, op amps with low or high rail features are needed, such as the TSV792 Rail-to-Rail op amp mentioned earlier, along with appropriate bandwidth and slew rate capabilities to track pulse width modulation


www.cieonline.co.uk


(PWM). ST’s rail-to-rail op amp portfolio encompasses multiple series that cover different voltage ranges, offering various combinations of power consumption and gain bandwidth. In cases involving strain gauges, thermocouples, RTD sensors, or resistive sensors, rail-to-rail inputs are often unnecessary. In addition, a low-noise op amp may be required for optimal performance in these applications. Current measurement: In circuits where sensors generate small currents, it is often necessary to choose an op amp with a low input bias current. For such applications, CMOS of JFET input amplifiers used in transimpedance amplification are well-suited, input offset voltage typically has minimal impact. When incorporating photodiode sensors into battery- powered circuits, like those found in communication systems, light curtains, smoke detectors, electrochemical gas sensors, or optical heart rate monitors, several factors come into play. Low power consumption becomes crucial to maximize battery life. Additionally, the op amp should be fast and capable of high slew rates, ensuring swift response and signal processing. The TSV7722 high bandwidth unity-gain-stable amplifier is well suited to these applications. Signal buffering: When interfacing an analog signal with an Analog-to-Digital Converter (ADC), several challenges may arise. One such challenge is the requirement of the ADC to charge input capacitors with a high current within a short period. To address this, an additional capacitor is often used at the output of the op amp. However, this approach can introduce stability issues and may necessitate the use of compensation techniques.


When selecting an op amp for an application designers will also want to avoid choosing a device which may go end of life in the short to medium term. To help avoid this scenario, most of STMicroelectronics newly developed high-performance op amps come with their 10-year longevity commitment, just look out for the logo on the ST product pages.


Design support


Anglia offers support for customer designs with free evaluation kits, demonstration boards and samples of STMicroelectronics products via the EZYsample service which is available to all registered Anglia Live account customers.


Anglia’s engineering team are also on hand to support designers, we can offer advice and support at component and system level. This expertise is available to assist customers with all aspects of their product design, providing hands on support and access to additional comprehensive STMicroelectronics resources which includes technical application notes and reference designs to help designers select the right product for their application. Visit www.


anglia-live.com to see the full range of STMicroelectronics products available from Anglia.


Components in Electronics July/August 2023 11


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