HG324

Battery life depends on operating voltage, duty cycle, and battery capacity. For example, with a CR2032 coin cell (220mAh), operating at 3.3V with all four amplifiers active: Total current = 4 × 40μA = 160μA. Battery life = 220mAh / 0.16mA = 1375 hours (about 57 days) continuous operation. With 10% duty cycle (typical for sensor sampling), life extends to 570 days. Using shutdown mode between samples can reduce average current to microamps, extending life to years. For always-on applications, consider using two amplifiers instead of four to halve current consumption.

Calculate battery life based on your duty cycle. Use shutdown mode for intermittent operation. Contact our FAE team for battery life optimization.

HG324 is guaranteed to operate down to 1.8V supply voltage, making it suitable for single-cell alkaline (nominal 1.5V, fresh 1.6V) and Li-ion coin cells. At 1.8V, the output can swing rail-to-rail (within 10mV), providing nearly 1.8V peak-to-peak output. Input common-mode range extends to ground and up to VCC - 1V. At 1.8V operation, GBW reduces slightly to about 1MHz, and slew rate to 0.7V/μs. For 1.5V alkaline cells, operation continues until cell voltage drops below 1.8V, which occurs near end-of-life.

HG324 works with single-cell batteries down to 1.8V. For 1.5V operation, contact our FAE team for alternative recommendations.

HG324 is excellent for high-impedance sensors due to its ultra-low input bias current of 1pA typical. This makes it ideal for pH sensors, photodiodes, glass electrodes, and other high-impedance sources where input current would cause significant errors. For example, with a 10MΩ source impedance and 1pA bias current, the error voltage is only 10μV. Compare this to standard op-amps with 100nA bias current, which would create 1V error. The CMOS input stage provides this ultra-low bias current while maintaining good noise performance for sensor applications.

HG324 is ideal for high-impedance sensors. For very high impedance (>100MΩ), contact our FAE team for specialized recommendations.

HG324 can drive capacitive loads up to 100pF without stability issues. For larger capacitive loads (up to 1000pF), an isolation resistor of 20-50Ω in series with the output prevents ringing and oscillation. The resistor isolates the capacitive load from the op-amp output, creating a zero that compensates the pole formed by the load capacitance. For driving large capacitive loads (>1000pF), consider using an output buffer stage or a dedicated power op-amp. In most sensor applications, 100pF drive capability is sufficient for cable capacitance and ADC input sampling.

Use isolation resistor for capacitive loads >100pF. Contact our FAE team for capacitive load driving solutions.

HG324 has input voltage noise density of 40nV/√Hz at 1kHz, which is typical for low-power CMOS op-amps. For a 10kHz bandwidth, total noise is approximately 4μV RMS. This is adequate for most sensor applications. Current noise is negligible due to the CMOS input (1pA bias current). For comparison, precision bipolar op-amps may have lower voltage noise (3-10nV/√Hz) but much higher current noise. In high-impedance applications, the low current noise of HG324 often results in better overall noise performance than bipolar alternatives.

For most sensor applications, HG324 noise is adequate. For very low noise requirements, contact our FAE team for precision op-amp recommendations.

HG324 features a shutdown pin that disables all four amplifiers when pulled low, reducing supply current to less than 1μA. When shutdown is high or floating, normal operation resumes. This is useful for duty-cycled applications where amplifiers are only needed during sampling. Typical wake-up time from shutdown is 10μs. To use: Connect shutdown pin to GPIO for software control; Pull high for normal operation, low for shutdown; For always-on operation, tie shutdown to VCC. Note that outputs go to high-impedance state during shutdown, so consider pull-up/pull-down resistors if defined state is needed.

Use shutdown pin for duty-cycled operation to extend battery life. Contact our FAE team for power management strategies.