Tiny nano-power op amp boosts sensing accuracy for minimal power

December 13, 2016 // By Graham Prophet
In a 1.2 x 1.3 mm outline and with typical current of 900 nA, the TSU111 nano-power op amp from STMicroelectronics can cut the size and energy needs of analogue circuits to the bare minimum in medical monitors, wearable electronics, gas detectors, pH sensors, infrared motion sensors, and payment tags.

The TSU111’s extremely low operating current, ST says, is comparable to the leakage current of some low-cost capacitors, and would take over 25 years to discharge a 220 mAh CR2032 cell. Hence the op amp can be designed-in with negligible impact on overall system energy management.

 

At the same time, the TSU111 outperforms other nano-power op amps with its input-offset voltage of 150 µV and 0.1-10 Hz noise of 3.6 µVp-p that ensure high accuracy in signal-conditioning circuits. A gain-bandwidth product (GBWP) of 11.5 kHz and a rail-to-rail input stage enable monitoring of environmental or biological signals. The very low input bias current of 10 pA helps minimize the effects of parasitic currents in sensing devices such as gas detectors or photodiodes.

 

The supply-voltage range of 1.5V to 5V allows the TSU111 to be powered from the same supply rail as logic circuitry thereby simplifying power-supply design and board layout. The low minimum voltage allows the device to run longer as the battery discharges, and simplifies use in equipment powered by energy-harvesting systems such as photovoltaic (PV) cells.

 

In the 1.2 x 1.3 mm DFN6 package or 2 x 2.1 mm SC70-5 (SOT323-5), the chip is priced from $0.69 (1000).

 

ST; www.st.com/tsu111-pr