Overview
The LOG114, produced by Texas Instruments, is a precision logarithmic amplifier designed for measuring low-level and wide dynamic range currents. It is particularly suited for applications in communications, lasers, medical, and industrial systems. The device computes the logarithm or log-ratio of an input current relative to a reference current, ensuring high precision over a wide dynamic range of input signals. It can operate on either bipolar (±5V) or single (+5V) supply and includes special temperature drift compensation circuitry for stable performance over a wide temperature range.
Key Specifications
| Parameter | Conditions | Min | Typ | Max | Units |
|---|---|---|---|---|---|
| Input Dynamic Range | 100 pA | 10 mA | |||
| Log Conformity Error (Initial) | 1 nA to 100 µA (5 decades) | 0.1% | 0.2% | 0.4% | % |
| Log Conformity Error (Initial) | 100 pA to 3.5 mA (7.5 decades) | 0.9% | % | ||
| Voltage Reference | 2.5 V | V | |||
| Quiescent Current | IO = 0 | ±10 mA | ±15 mA | mA | |
| Temperature Range (Specification) | −5°C | +75°C | °C | ||
| Temperature Range (Operating) | −40°C | +85°C | °C | ||
| Package | QFN-16 (4mm x 4mm) |
Key Features
- Tiny form factor suitable for high-density systems.
- Precision operation on a single supply (+5V) or dual supply (±5V).
- Fast response over eight decades of input current (100 pA to 10 mA).
- Stable performance over a wide temperature range with temperature drift compensation.
- Low quiescent current of ±10 mA.
- On-chip 2.5V reference for generating the reference current.
- Two additional amplifiers (A4 and A5) for scaling, offsetting, filtering, and other functions.
Applications
- Optical communications: Erbium-doped fiber optic amplifier (EDFA) and laser optical density measurement.
- Photodiode signal compression amplifier.
- Logarithmic and log-ratio functions.
- Analog signal compression in front of analog-to-digital converters (ADCs).
- Absorbance measurement.
Q & A
- What is the primary function of the LOG114?
The LOG114 is a precision logarithmic amplifier that computes the logarithm or log-ratio of an input current relative to a reference current.
- What is the input dynamic range of the LOG114?
The input dynamic range is from 100 pA to 10 mA, spanning eight decades.
- Can the LOG114 operate on a single supply or dual supply?
Yes, it can operate on either a single supply (+5V) or a dual supply (±5V).
- What is the quiescent current of the LOG114?
The quiescent current is ±10 mA when IO = 0.
- What is the temperature range for the LOG114?
The specified temperature range is −5°C to +75°C, and it can operate from −40°C to +85°C.
- What package type is the LOG114 available in?
The LOG114 is available in a QFN-16 package (4mm x 4mm).
- What additional features does the LOG114 include for signal processing?
The LOG114 includes two additional amplifiers (A4 and A5) for scaling, offsetting, filtering, and other functions.
- How does the LOG114 handle temperature drift?
The LOG114 includes special temperature drift compensation circuitry to ensure stable performance over a wide temperature range.
- What are some common applications of the LOG114?
Common applications include optical communications, photodiode signal compression, logarithmic and log-ratio functions, analog signal compression in front of ADCs, and absorbance measurement.
- How can the output of the LOG114 be adjusted?
The output can be scaled and offset using one of the available additional amplifiers to match a wide variety of ADC input ranges.
