LV2622_15 Datasheet, PDF (5/8 Pages) Unisonic Technologies – LOW VOLTAGE RAIL-TO-RAIL I/O CMOS DUAL OP AMPS

LV2622
Preliminary
LINEAR INTEGRATED CIRCUIT
„ APPLICATION NOTES
Driving a Capacitive Load
The UTC LV2622 can directly drive 1000pF in unity-gain without oscillation. The unity-gain follower (buffer) is the
most sensitive configuration to capacitive loading. When the amplifier is configured in this manner, capacitive
loading directly on the output will decrease the device’s phase margin leading to high frequency ringing
or oscillations. It is recommended that an isolation resistor (R_ISO) is placed in series with the output of the
amplifier when the greater capacitive load is required. The circuit is shown in Figure 1. The R_ISO and the load
capacitor C_L form a zero to increase stability, but this method results in a loss of gain accuracy for R_ISO dividing the
voltage with R_LOAD.
The circuit in Figure 2 provides DC accuracy and AC stability. To increase the DC accuracy, R_F should be
connected between the inverting input and the output. To preserve the phase margin in the overall feedback loop, C_F
is required and can compensate the loss of phase margin together with R_Iso by feeding the high frequency
component of the output signal back to the amplifier’s inverting input
.
C_F
-
UTC LV2622
V_IN
+ ^1/2
R_F
R_ISO
C_L
V_OUT
R_L
Figure 2. Indirectly Driving Heavy Capacitive Load with DC Accuracy
For no-buffer configuration, there are two others ways to increase the phase margin: (a) by increasing the
amplifier’s gain or (b) by placing a capacitor in parallel with the feedback resistor to counteract the parasitic
capacitance associated with inverting node.
UNISONIC TECHNOLOGIES CO., LTD
www.unisonic.com.tw
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QW-R102-045.a