Low-Cost, High-Speed, SOT23, Single-Supply
Op Amps with Rail-to-Rail Outputs
MAX4012/MAX4016/MAX4018/MAX4020
_______________Detailed Description
The MAX4012/MAX4016/MAX4018/MAX4020 are sin-
gle-supply, rail-to-rail, voltage-feedback amplifiers that
employ current-feedback techniques to achieve
600V/µs slew rates and 200MHz bandwidths. Excellent
harmonic distortion and differential gain/phase perfor-
mance make these amplifiers an ideal choice for a wide
variety of video and RF signal-processing applications.
The output voltage swing comes to within 50mV of each
supply rail. Local feedback around the output stage
assures low open-loop output impedance to reduce
gain sensitivity to load variations. This feedback also
produces demand-driven current bias to the output
transistors for ±120mA drive capability, while constrain-
ing total supply current to less than 7mA. The input
stage permits common-mode voltages beyond the nega-
tive supply and to within 2.25V of the positive supply rail.
cuit formed by the parasitic feedback capacitance and
inductance.
__________Applications Information
Choosing Resistor Values
Unity-Gain Configuration
The MAX4012/MAX4016/MAX4018/MAX4020 are inter-
nally compensated for unity gain. When configured for
unity gain, the devices require a 24Ω resistor (R
F
) in
series with the feedback path. This resistor improves
AC response by reducing the Q of the parallel LC cir-
Inverting and Noninverting Configurations
Select the gain-setting feedback (R
F
) and input (R
G
)
resistor values to fit your application. Large resistor val-
ues increase voltage noise and interact with the amplifi-
er’s input and PC board capacitance. This can
generate undesirable poles and zeros and decrease
bandwidth or cause oscillations. For example, a nonin-
verting gain-of-two configuration (R
F
= R
G
) using 1kΩ
resistors, combined with 1pF of amplifier input capaci-
tance and 1pF of PC board capacitance, causes a pole
at 159MHz. Since this pole is within the amplifier band-
width, it jeopardizes stability. Reducing the 1kΩ resis-
tors to 100Ω extends the pole frequency to 1.59GHz,
but could limit output swing by adding 200Ω in parallel
with the amplifier’s load resistor. Table 1 shows sug-
gested feedback, gain resistors, and bandwidth for
several gain values in the configurations shown in
Figures 1a and 1b.
Layout and Power-Supply Bypassing
These amplifiers operate from a single +3.3V to +11V
power supply or from dual supplies to ±5.5V. For single-
supply operation, bypass V
CC
to ground with a 0.1µF
capacitor as close to the pin as possible. If operating with
dual supplies, bypass each supply with a 0.1µF capacitor.
R
G
R
F
IN
R
TO
MAX40_ _
R
G
R
F
V
OUT
R
TIN
MAX40_ _
R
TO
V
OUT
IN
R
TIN
V
OUT
= [1+ (R
F
/ R
G
)] V
IN
R
O
R
S
V
OUT
= -(R
F
/ R
G
) V
IN
R
O
Figure 1a. Noninverting Gain Configuration
Figure 1b. Inverting Gain Configuration
10
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