_______________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.

__________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 24

series with the feedback path. This resistor improves

AC response by reducing the Q of the parallel LC cir-

cuit formed by the parasitic feedback capacitance and

inductance.

Inverting and Noninverting Configurations

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-

Ω

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 1k

Ω resis-

tors to 100

Ω extends the pole frequency to 1.59GHz,

but could limit output swing by adding 200

Ω 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-

capacitor as close to the pin as possible. If operating with

dual supplies, bypass each supply with a 0.1µF capacitor.

Low-Cost, High-Speed, SOT23, Single-Supply

Op Amps with Rail-to-Rail Outputs

10

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IN

MAX40_ _

IN

MAX40_ _

Figure 1a. Noninverting Gain Configuration

Figure 1b. Inverting Gain Configuration