AD85052 データシートの表示（PDF） - Analog Devices

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AD85052

Operational Amplifiers Selection Guide

Analog Devices 

Amplifier Design Technology

Clamp Amplifiers

Clamp amplifiers allow the designer to specify a high (VCH) and low (VCL)

output clamp voltage so the output signal will clamp at the specified

levels. Analog Devices’ unique CLAMPIN™ input clamp architecture offers

significant improvement in clamp performance compared to traditional

output clamping devices, minimizing clamp error and distortion in the

clamp region.

Common-Mode Linearized Amplifiers

Increasing the linear input range of the input stage optimizes operational

amplifier large signal distortion. This can be accomplished through the

use of architectures such as degenerated differential structures and

class AB input stages, both of which increase noise and lower precision.

An alternate method is to linearize using a common-mode structure

whose noise is rejected by the inherent differential nature of the input

stage while also maintaining such precision metrics as CMRR, PSRR, and

VOS. Analog Devices has numerous new amplifiers that now feature this

new technology and has patented the common-mode linearized input

architecture.

Current Feedback Amplifiers

Current feedback amplifiers are primarily used in applications that require

very high speed operation, large slew rates, and low distortion. The

fundamental concept is based on the fact that, in bipolar transistor circuits,

currents can be switched faster than voltages, all other things being equal.

Unlike voltage feedback amplifiers (VFB), CFB amplifiers do not have

balanced inputs. Instead, the noninverting input is high impedance, and

the inverting input is low impedance. The open-loop gain of the CFB is

measured in units of V (transimpedance gain) rather than V/V as for VFB

amplifiers. Also, the value of the feedback resistor plays a direct role in the

CFB’s stability. Therefore, adhering to the recommended feedback resistor

suggested in the data sheet is highly recommended.

Differential Amplifiers

Differential amplifiers allow the process of single-ended input to

complementary differential outputs or differential inputs to differential

outputs. These amplifiers feature two separate feedback loops to control

the differential and common-mode output voltages. Analog Devices’

differential amplifiers are configured with a VOCM pin, which can be easily

adjusted for setting output common-mode voltage. This provides a

convenient solution when interfacing with analog-to-digital converters

(ADCs). ADI also offers a series of differential receiver products that

convert differential input signals to single-ended output.

Quad Core (H Bridge)

Analog Devices has patented the quad core architecture, which supplies

current on-demand to charge and discharge the internal dominant pole

capacitor, while allowing the quiescent current to be small. This patented

architecture enables amplifiers to provide high slew rates with low

distortion at low supply currents.

Overvoltage Protection (OVP) Amplifiers

An OVP amplifier is the most robust solution to protect the amplifier and

entire circuitry from outside the rail input voltages due to manufacturing

shorts, power supply timing, or human error. OVP is able to protect real

estate from various unexpected errors, which in turns save time and

money. OVP amplifiers require no external circuitry to provide protection.

Zero-Drift Amplifiers

Zero-drift amplifiers dynamically correct the offset voltage to achieve

nanovolt-level offsets and extremely low offset drifts due to time and

temperature. The 1/f noise, seen as a dc error, is also removed. Zero-drift

amplifiers provide many benefits to designers, as temperature drift and

1/f noise, always nuisances in the system, are otherwise very difficult to

eliminate. In addition, zero-drift amplifiers have higher open-loop gain,

power supply rejection, and common-mode rejection as compared to

standard amplifiers; and their overall output error is less than that

obtained by a standard precision amplifier in the same configuration.

Zero Input Crossover Distortion (ZCO) Amplifiers

Traditional rail-to-rail input amplifiers have an input stage that comprises

two differential pairs, a p-type and an n-type. During the transition of the

input common-mode voltage from the lower to the higher supply voltage,

one of the differential pairs turns off and the other turns on. This transition

causes crossover distortion. Zero input crossover distortion (ZCO) amplifiers

solve this problem by integrating an on-chip charge pump. The charge

pump increases the internal supply voltage, thus providing more headroom

to the input stage. This allows the input stage to handle a wider range of

input voltages (rail to rail) without using a second differential pair. As a

result, crossover distortion is avoided.

www.analog.com/opamps | 5

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