Precision Resistor Network for

Programmable Instrumentation Amplifiers

6

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Applications Information

The MAX5426 is ideal for programmable instrumentation

amplifier applications. The typical application circuit of

Figure 1 uses the MAX5426 in classical instrumentation

amplifier configurations. Two digital inputs set the gain to

1, 2, 4, or 8.

Op Amp Selection Guidelines

Selection of an op amp for instrumentation amplifier cir-

cuits depends on the accuracy requirements of the

specific application. General guidelines are to choose

an op amp with sufficient open-loop gain, low input-off-

set voltage, and a high common-mode rejection ratio.

High open-loop gain is needed to increase the gain

accuracy, while low input-offset voltage and low input-

offset current help meet gain and offset requirements.

Other parameters such as low input capacitance, low

input bias current, high input common-mode range,

and low noise often need to be considered for a wide

input voltage range stability and AC considerations.

The MAX427 is an excellent choice to use with the

MAX5426.

Stereo Audio-Taper Attenuator

Figure 2 shows the application of the MAX5426 as a dual

attenuator that can be used in stereo audio systems.

Power Supplies and Bypassing

The MAX5426 operates from dual ±5V to ±15V sup-

plies. In many applications the MAX5426 does not

require bypassing. If power-supply noise is excessive,

GND.

Layout Concerns

For best performance, reduce parasitic board capaci-

tance by minimizing the circuit board trace from ampli-

fier outputs to inverting inputs. Also choose op amps

with low input capacitance.

CM

FB2

INDIF-

OUT2

INDIF+

OUT

OFFSET

GND

D1

D0

FB1

OUT1

MAX5426

MAX427

MAX427

MAX427

Figure 1. Programmable Instrumentation Amplifier Using MAX5426