MAX4187EEE datasheet(17/24 Pages) MAXIM

17 / 24 page

Single/Dual/Quad, 270MHz, 1mA, SOT23,

Current-Feedback Amplifiers with Shutdown

______________________________________________________________________________________

Table 1. Recommended Component Values

Choosing Feedback and Gain Resistors

The optimum value of the external-feedback (RF) and

gain-setting (RG) resistors used with the MAX4180–

MAX4187 depends on the closed-loop gain and the

application circuit’s load. Table 1 lists the optimum

resistor values for some specific gain configurations.

One-percent resistor values are preferred to maintain

consistency over a wide range of production lots.

Figures 4a and 4b show the standard inverting and

noninverting configurations. Note that the noninverting

circuit gain (Figure 4) is 1 plus the magnitude of the

inverting closed-loop gain. Otherwise, the two circuits

are identical.

DC and Noise Errors

Several major error sources must be considered in any

op amp. These apply equally to the MAX4180–

MAX4187. Offset-error terms are given by the equation

below. Voltage and current-noise errors are root-square

summed and are therefore computed separately. In

Figure 5, the total output offset voltage is determined by

the following factors:

• The input offset voltage (VOS) times the closed-loop

gain (1 = RF / RG).

• The positive input bias current (IB+) times the source

resistor (RS) (usually 50Ω or 75Ω), plus the negative

input bias current (IB-) times the parallel combination

of RG and RF. In current-feedback amplifiers, the

input bias currents at the IN+ and IN- terminals do

not track each other and may have opposite polarity,

so there is no benefit to matching the resistance at

both inputs.

The equation for the total DC error at the output is:

The total output-referred noise voltage is:

n OUT

()







 ()

[] + ()

[] +()

+−

VOUT

() + ()

() +

[] +









+−

245

1.2k

RL = 1kΩ

190

680

RL =

100

Ω

-3dB BW (MHz)

190

820

RL = 150Ω

RG (Ω)

RF (Ω)

COMPONENT/BW

105

180

750

RL =

Ω/150Ω

AV = +10V/V

205

—

RL =

150

Ω

120

270

—

2.4k

RL = 1kΩ

220

910

RL =

Ω/150Ω

AV = +5V/V

200

—

560

RL =

100

Ω

AV = +2V/V

AV = +1V/V

MAX4180

MAX4181

AV = +2V/V

245

RL =

Ω

160

MAX4182/MAX4183

620

RL =

100

Ω

-3dB BW

(MHz)

190

680

RL =

150

Ω

RG (Ω)

RF (Ω)

COMPONENT/

AV = +2V/V

245

1.1k

RL =

Ω

175

MAX4186

680

RL =

100

Ω

190

750

RL =

150

Ω

AV = +1V/V

270

—

1.6k

RL =

Ω

200

MAX4187

—

680

RL =

100

Ω

205

—

910

RL =

150

Ω

AV = +1V/V

270

—

1.5k

RL =

Ω

180

MAX4184/MAX4185

—

620

RL =

100

Ω

205

—

750

RL =

150

Ω

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