MAX1886
Detailed Description
The MAX1886 operational transconductance amplifier
(OTA) provides high-current output that is ideal for dri-
ving capacitive loads such as the backplane of a TFT
LCD panel. The positive feedback input, FB+, allows
common-mode biasing to mid-supply, or other VCOM
voltage.
The MAX1886 unity-gain bandwidth is GBW = g
m
/C
OUT
where g
m
is the amplifier’s transconductance.
Transconductance is the ratio of the output current to
the input voltage. The gain of the amplifier is dependent
upon the load. The MAX1886 requires only a small
0.47µF ceramic output capacitor for stability. The band-
width is inversely proportional to the output capacitor,
so large capacitive loads improve stability; however,
lower bandwidth decreases the buffer’s transient
response time. To improve the transient response
times, the MAX1886’s transconductance increases as
the output current increases (see Typical Operating
Characteristics).
Applications Information
Output Filter Capacitor
The MAX1886 requires a minimum of 0.47µF output
capacitance placed close to OUT. To ensure buffer sta-
bility, the output capacitor ESR must be 50mΩ or lower.
Ceramic capacitors are an excellent choice.
Input Bypass Capacitor
The MAX1886 requires a 0.47µF input bypass capacitor
(C2) close to the V
CC
supply input (see Figure 2). Place
the MAX1886 close to the preceding voltage regulator
output capacitor so that the MAX1886 shares the same
capacitor (C1). Minimize trace length and use wide
High-Current VCOM Drive Buffer
4 _______________________________________________________________________________________
Output of Buffer Amplifier. Requires a minimum 0.47µF ceramic filter capacitor to GND. Place the
capacitor close to OUT.
Voltage-Supply Input. Bypass to GND with a 0.47µF capacitor close to the pin. Use the output
capacitor of the preceding voltage regulator as the additional filter capacitor.
