Reference Design  For LCR Meter Utilizing Auto-Balancing 

By integrating the OPA2810 and BUF634A, the system ensures accuracy, stability, and extensive impedance protection, making it a dependable alternative for semiconductor testing, digital multimeters, and vector community analyzers.

The target of any take a look at and measurement system is to measure a tool below take a look at (DUT) with minimal complexity whereas making certain that launched errors stay considerably smaller than these current within the DUT. For impedance measurements, a number of methods exist, every providing tradeoffs between measurement accuracy, complexity, and frequency vary. 

This reference design, TIDA-060029 by Texas Devices employs an auto-balancing impedance measurement methodology, chosen for its glorious accuracy over a broad impedance vary with out requiring guide tuning. Auto-balancing impedance measurement circuits will be tough to stabilize since their stability will depend on each the part sort and worth. Due to this fact, an inherently secure circuit is important, whatever the measured part’s traits. This design presents a strong analog signal-chain answer with 0.1% accuracy, making it superb for LCR meter functions. It measures inductance (L), capacitance (C), and resistance (R) throughout a large impedance vary from 1 Ω to 10 MΩ, operates at frequencies as much as 100 kHz, and has been examined at 100 Hz, 1 kHz, 10 kHz, and 100 kHz. The circuit is inherently secure, making certain exact and constant impedance measurements. 

– Commercial –

This reference design is well-suited for functions corresponding to digital multimeters (DMMs), impedance and vector community analyzers, and semiconductor manufacturing and testing. A key part on this design is the OPA2810, a dual-channel, FET-input voltage-feedback operational amplifier with a particularly low enter bias present of two pA, which is essential for high-impedance measurements as much as 10 MΩ. The OPA2810 is unity-gain secure, that includes a 105 MHz small-signal bandwidth, 120 dB open-loop acquire (Aol), and sustaining over 60 dB at frequencies beneath 100 kHz. Its gain-bandwidth product (GBW) of 70 MHz ensures correct sign processing, whereas the ±13.5 V provide voltage optimizes distortion efficiency. Moreover, its low voltage noise (6 nV/√Hz) minimizes sign degradation, additional enhancing measurement accuracy. A excessive Aol worth ensures that the inverting enter voltage stays near zero, decreasing measurement errors and making the OPA2810 an important part on this impedance measurement system.

The BUF634A, a high-speed, wide-bandwidth unity-gain buffer, is optionally utilized in a composite loop with the OPA2810 to extend the output present functionality from 100 mA to 250 mA. It supplies two selectable bandwidth choices, 35 MHz (low bandwidth) and 210 MHz (excessive bandwidth), providing flexibility primarily based on utility necessities. Though not necessary, the BUF634A enhances the circuit’s drive functionality, making it helpful in eventualities the place increased present output is required. This reference design successfully demonstrates a high-precision auto-balancing impedance measurement answer for LCR meters. 

– Commercial –

TI has examined this reference design. It comes with a invoice of supplies (BOM), schematics, meeting drawing, printed circuit board (PCB) structure, and extra. The corporate’s web site has extra knowledge in regards to the reference design. To learn extra about this reference design, click on right here.