Texas Instruments

The LOG112 and LOG2112 are versatile integrated circuits that compute the logarithm or log ratio of an input current relative to a reference current. VLOGOUTof the LOG112 and LOG2112 are trimmed to 0.5V per decade of input current, ensuring high precision over a wide dynamic range of input signals. The LOG112 and LOG2112 features a 2.5V voltage reference that may be used to generate a precision current reference using an external resistor. Low DC offset voltage and temperature drift allow accurate measurement of low-level signals over the specified temperature range of –5°C to +75°C. The LOG112 and LOG2112 are versatile integrated circuits that compute the logarithm or log ratio of an input current relative to a reference current. VLOGOUTof the LOG112 and LOG2112 are trimmed to 0.5V per decade of input current, ensuring high precision over a wide dynamic range of input signals. The LOG112 and LOG2112 features a 2.5V voltage reference that may be used to generate a precision current reference using an external resistor. Low DC offset voltage and temperature drift allow accurate measurement of low-level signals over the specified temperature range of –5°C to +75°C.

The LOG114 is specifically designed for measuring low-level and wide dynamic range currents in communications, lasers, medical, and industrial systems. The device computes the logarithm or log-ratio of an input current or voltage relative to a reference current or voltage (logarithmic transimpedance amplifier). High precision is ensured over a wide dynamic range of input signals on either bipolar (±5V) or single (5V) supply. Special temperature drift compensation circuitry is included on-chip. In log-ratio applications, the signal current may be from a high impedance source such as a photodiode or resistor in series with a low impedance voltage source. The reference current is provided by a resistor in series with a precision internal voltage reference, photo diode, or active current source. The output signal at VLOGOUT has a scale factor of 0.375V/decade of input current, which limits the output so that it fits within a 5V or 10V range. The output can be scaled and offset with one of the available additional amplifiers, so it matches a wide variety of ADC input ranges. Stable DC performance allows accurate measurement of low-level signals over a wide temperature range. The LOG114 is specified over a −5°C to 75°C temperature range and can operate from −40°C to 85°C. The LOG114 is specifically designed for measuring low-level and wide dynamic range currents in communications, lasers, medical, and industrial systems. The device computes the logarithm or log-ratio of an input current or voltage relative to a reference current or voltage (logarithmic transimpedance amplifier). High precision is ensured over a wide dynamic range of input signals on either bipolar (±5V) or single (5V) supply. Special temperature drift compensation circuitry is included on-chip. In log-ratio applications, the signal current may be from a high impedance source such as a photodiode or resistor in series with a low impedance voltage source. The reference current is provided by a resistor in series with a precision internal voltage reference, photo diode, or active current source. The output signal at VLOGOUT has a scale factor of 0.375V/decade of input current, which limits the output so that it fits within a 5V or 10V range. The output can be scaled and offset with one of the available additional amplifiers, so it matches a wide variety of ADC input ranges. Stable DC performance allows accurate measurement of low-level signals over a wide temperature range. The LOG114 is specified over a −5°C to 75°C temperature range and can operate from −40°C to 85°C.

The LOG112 and LOG2112 are versatile integrated circuits that compute the logarithm or log ratio of an input current relative to a reference current. VLOGOUTof the LOG112 and LOG2112 are trimmed to 0.5V per decade of input current, ensuring high precision over a wide dynamic range of input signals. The LOG112 and LOG2112 features a 2.5V voltage reference that may be used to generate a precision current reference using an external resistor. Low DC offset voltage and temperature drift allow accurate measurement of low-level signals over the specified temperature range of –5°C to +75°C. The LOG112 and LOG2112 are versatile integrated circuits that compute the logarithm or log ratio of an input current relative to a reference current. VLOGOUTof the LOG112 and LOG2112 are trimmed to 0.5V per decade of input current, ensuring high precision over a wide dynamic range of input signals. The LOG112 and LOG2112 features a 2.5V voltage reference that may be used to generate a precision current reference using an external resistor. Low DC offset voltage and temperature drift allow accurate measurement of low-level signals over the specified temperature range of –5°C to +75°C.