Datasheet GS8551, GS8552, GS8554 (Gainsil) - 6

GS8551/8552/8554 Application Note Size GS855X series op amps are unity-gain stable and suitable for a wide range of general-purpose applications. The small footprints of the GS855X series packages save space on printed circuit boards and enable the design of smaller electronic products. Power Supply Bypassing and Board Layout GS855X series operates from a single 1.8V to 5.5V supply or dual ±0.9V to ±2.75V supplies. For best performance, a 0.1µF ceramic capacitor should be placed close to the VDD pin in single supply operation. For dual supply operation, both VDD and VSS supplies should be bypassed to ground with separate 0.1µF ceramic capacitors. Low Supply Current The low supply current (typical 180µA per channel) of GS855X series will help to maximize battery life. They are ideal for battery powered systems. Operating Voltage GS855X series operate under wide input supply voltage (1.8V to 5.5V). In addition, all temperature specifications apply from -40 oC to +125 oC. Most behavior remains unchanged throughout the full operating voltage range. These guarantees ensure operation throughout the single Li-Ion battery lifetime. Rail-to-Rail Input The input common-mode range of GS855X series extends 100mV beyond the supply rails (VSS-0.1V to VDD+0.1V). This is achieved by using complementary input stage. For normal operation, inputs should be limited to this range. Rail-to-Rail Output Rail-to-Rail output swing provides maximum possible dynamic range at the output. This is particularly important when operating in low supply voltages. The output voltage of GS855X series can typically swing to less than 5mV from supply rail in light resistive loads (>100kΩ), and 60mV of supply rail in moderate resistive loads (10kΩ). Capacitive Load Tolerance The GS855x family is optimized for bandwidth and speed, not for driving capacitive loads. Output capacitance will create a pole in the amplifier’s feedback path, leading to excessive peaking and potential oscillation. If dealing with load capacitance is a requirement of the application, the two strategies to consider are (1) using a small resistor in series with the amplifier’s output and the load capacitance and (2) reducing the bandwidth of the amplifier’s feedback loop by increasing the overall noise gain. Figure 2. shows a unity gain follower using the series resistor strategy. The resistor isolates the output from the capacitance and, more importantly, creates a zero in the feedback path that compensates for the pole created by the output capacitance. Figure 2. Indirectly Driving a Capacitive Load Using Isolation Resistor March 2020-REV_V2 6/14