SOT23, Rail-to-Rail, Fixed-Gain

GainAmps/Open-Loop Op Amps

______________________________________________________________________________________

13

GainAmp Signal Coupling

and Configurations

Common op-amp configurations include both nonin-

verting and inverting amplifiers. Figures 5–8 show vari-

ous single and dual-supply circuit configurations.

Single-supply systems benefit from a midsupply bias

on the noninverting input (provided internally on

MAX4175/MAX4275), as this produces a quiescent DC

level at the center of the rail-to-rail output stage signal

swing. For dual-supply systems, ground-referenced

signals may be DC-coupled into the inverting or non-

inverting inputs.

IN_+ Filter on MAX4175/MAX4275

ples power-supply noise directly to the op amp’s nonin-

verting input. To minimize high-frequency power-supply

noise coupling, add a 1µF to 0.1µF capacitor from IN+

to ground to create a lowpass filter (Figure 6). The low-

pass filter resulting from the internal bias resistors and

added capacitor can help eliminate higher frequency

power-supply noise coupling through the noninverting

input.

MAX4281

Figure 4. Single-Supply, DC-Coupled Inverting Amplifier with

Negative Input Voltage

MAX4175

0.1

µF

(

2

Figure 6. Single-Supply, AC-Coupled Inverting Amplifier

MAX4174

(

Figure 5. Dual-Supply, DC-Coupled Inverting Amplifier

MAX4174

Figure 7. Dual-Supply, AC-Coupled Noninverting Amplifier