Texas Instruments LOG200 Precision High-Speed Logarithmic Amplifier
Texas Instruments LOG200 Precision High-Speed Logarithmic Amplifier is a wide-dynamic-range current-to-voltage amplifier designed to optimize current measurements across 160dB of dynamic range. The device has unparalleled accuracy and speed for medical diagnostics, optical communications, and industrial process-control measurements. The LOG200 features two logarithmic amplifiers and a high-accuracy differential amplifier that converts current signals into a voltage representing the log-compressed ratio of the two currents. The current inputs are designed to feature a highly accurate reference signal from one input and a high-speed response on the other input. This feature allows for a unique combination of high logarithmic conformity and fast transient response.
The LOG200's ratio is internally set to 250mV/decade of current-to-voltage conversion. The device integrates an uncommitted high-speed amplifier to allow the output to be configured for filtered or differential responses, with a fast settling time to drive successive approximation analog-to-digital converters (SAR ADCs). The LOG200 also features a separate reference voltage and reference current designed to configure the device for optimized input current and common-mode voltages.
The Texas Instruments LOG200 can be powered in a dual-supply (±2.25V to ±6.3V) or single-supply (4.5V to 12.6V) configuration and is specified from –40°C to +125°C.
Features
- Ultra-fast transient response to low current levels
- Settling time for 10nA to 100nA step of 240ns rising, 620ns falling (typ.)
- Settling time for 100nA to 1µA step of 60ns rising, 150ns falling (typ.)
- Wide dynamic range of 10pA to 10mA (180dB) that is specified from 100pA to 10mA (160dB)
- High signal bandwidth
- 20MHz at 10µA to 10mA
- 6.3MHz at 1µA
- 90kHz at 1nA
- A high-accuracy transfer function of 0.2% max log conformity error (10nA to 100µA)
- Integrated reference current (1µA) and reference voltages (2.5V and 1.65V)
- Additional auxiliary high-speed op amp for differential ADC drive, single-ended gain or filter blocks, and other peripheral functions
- Single supply (4.5V to 12.6V) or dual supply (±2.25V to ±6.3V) operation
- A specified temperature range of –40°C to +125°C
- 3mm × 3mm VQFN small package
Applications
- Optical modules
- Inter-DC interconnect
- Optical network terminal unit
- Chemistry/gas analyzer
- Erbium-doped fiber optic amplifier (EDFA)
Functional Block Diagram
Development Tool
Texas Instruments LOG200EVM Amplifier Evaluation Module (EVM)
A platform for evaluating the LOG200, a precision, high-speed logarithmic amplifier.