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MAX4475_12 Datasheet, PDF (9/21 Pages) Maxim Integrated Products – SOT23, Low-Noise, Low-Distortion, Wide-Band, Rail-to-Rail Op Amps
MAX4475–MAX4478/MAX4488/MAX4489
SOT23, Low-Noise, Low-Distortion,
Wide-Band, Rail-to-Rail Op Amps
Detailed Description
The MAX4475–MAX4478/MAX4488/MAX4489 single-
supply operational amplifiers feature ultra-low noise
and distortion. Their low distortion and low noise make
them ideal for use as preamplifiers in wide dynamic-
range applications, such as 16-bit analog-to-digital
converters (see Typical Operating Circuit). Their high-
input impedance and low noise are also useful for sig-
nal conditioning of high-impedance sources, such as
piezoelectric transducers.
These devices have true rail-to-rail ouput operation,
drive loads as low as 1kΩ while maintining DC accura-
cy, and can drive capactive loads up to 200pF without
oscillation. The input common-mode voltage range
extends from (VDD - 1.6V) to 200mV below the negative
rail. The push-pull output stage maintains excellent DC
characteristics, while delivering up to ±5mA of current.
The MAX4475–MAX4478 are unity-gain stable, while
the MAX4488/MAX4489 have a higher slew rate and
are stable for gains ≥ 5V/V. The MAX4475/MAX4488
feature a low-power shutdown mode, which reduces
the supply current to 0.01µA and disables the outputs.
Low Distortion
Many factors can affect the noise and distortion that the
device contributes to the input signal. The following
guidelines offer valuable information on the impact of
design choices on Total Harmonic Distortion (THD).
Choosing proper feedback and gain resistor values for
a particular application can be a very important factor
in reducing THD. In general, the smaller the closed-
loop gain, the smaller the THD generated, especially
when driving heavy resistive loads. The THD of the part
normally increases at approximately 20dB per decade,
as a function of frequency. Operating the device near
or above the full-power bandwidth significantly
degrades distortion.
Referencing the load to either supply also improves the
part’s distortion performance, because only one of the
MOSFETs of the push-pull output stage drives the out-
put. Referencing the load to midsupply increases the
part’s distortion for a given load and feedback setting.
(See the Total Harmonic Distortion vs. Frequency graph
in the Typical Operating Characteristics.)
For gains ≥ 5V/V, the decompensated devices
MAX4488/MAX4489 deliver the best distortion perfor-
mance, since they have a higher slew rate and provide
a higher amount of loop gain for a given closed-loop
gain setting. Capacitive loads below 100pF do not sig-
nificantly affect distortion results. Distortion perfor-
mance is relatively constant over supply voltages.
CZ
RF
RG
VIN
VOUT
Figure 1. Adding Feed-Forward Compensation
100mV
AV = +2
RF = RG = 100kΩ
0V
VIN
100mV/div
VOUT
100mV/div
2µs/div
Figure 2a. Pulse Response with No Feed-Forward
Compensation
AV = +2
RF = RG = 100kΩ
VIN
100mV/div
VOUT
100mV/div
2µs/div
Figure 2b. Pulse Response with 10pF Feed-Forward
Compensation
Maxim Integrated
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