7.4.1 Output Characteristics

As already mentioned the output is rail-to-rail. When loading the output with a 10-kΩ resistor the maximum swing of the output is typically 6 mV from the positive and negative rail.

The output of the LMV83x can drive currents up to 30 mA at 3.3 V and even up to 65 mA at 5 V.

The LMV83x can be connected as noninverting unity-gain amplifiers. This configuration is the most sensitive to capacitive loading. The combination of a capacitive load placed at the output of an amplifier along with the output impedance of the amplifier creates a phase lag, which reduces the phase margin of the amplifier. If the phase margin is significantly reduced, the response will be under damped which causes peaking in the transfer and, when there is too much peaking, the operational amplifier might start oscillating. The LMV83x can directly drive capacitive loads up to 200 pF without any stability issues. In order to drive heavier capacitive loads, an isolation resistor, R_ISO, should be used, as shown in Figure 46. By using this isolation resistor, the capacitive load is isolated from the output of the amplifier, and hence, the pole caused by C_L is no longer in the feedback loop. The larger the value of R_ISO, the more stable the amplifier will be. If the value of R_ISO is sufficiently large, the feedback loop will be stable, independent of the value of C_L. However, larger values of R_ISO result in reduced output swing and reduced output current drive.

Figure 46. Isolating Capacitive Load

A resistor value of around 150 Ω would be sufficient. As an example some values are given in Table 1, for 5 V.