AD8610BR-REEL Просмотр технического описания (PDF) - Analog Devices

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AD8610BR-REEL

Precision, Very Low Noise, Low Input Bias Current, Wide Bandwidth JFET Operational Amplifier

Analog Devices 

AD8610/AD8620

The slew rate of the AD8610/AD8620 is double that of the

OPA627 when configured in a unity gain of +1 (see Figure 53

and Figure 54).

VS = ±13V

RL = 2kΩ

G = +1

SR = 85V/µs

TIME (400ns/DIV)

Figure 53. +Slew Rate of AD8610/AD8620 in Unity Gain of +1

VS = ±13V

RL = 2kΩ

G = +1

SR = 23V/µs

TIME (400ns/DIV)

Figure 54. +Slew Rate of OPA627 in Unity Gain of +1

The slew rate of an amplifier determines the maximum frequency

at which it can respond to a large signal input. This frequency

(known as full-power bandwidth or FPBW) can be calculated

for a given distortion (for example, 1%) from the equation:

FPBW = SR

( ) 2π × VPEAK

CH1 = 20.8V p-p

0V

Input Overvoltage Protection

When the input of an amplifier is driven below VEE or above

VCC by more than one VBE, large currents flow from the sub­

strate through the negative supply (V–) or the positive supply

(V+), respectively, to the input pins and can destroy the device.

If the input source can deliver larger currents than the maximum

forward current of the diode (>5 mA), a series resistor can be

added to protect the inputs. With its very low input bias and

offset current, a large series resistor can be placed in front of

the AD8610/AD8620 inputs to limit current to below damaging

levels. Series resistance of 10 kΩ generates less than 25 μV of offset.

This 10 kΩ allows input voltages more than 5 V beyond either

power supply. Thermal noise generated by the resistor adds

7.5 nV/√Hz to the noise of the AD8610/AD8620. For the AD8610/

AD8620, differential voltages equal to the supply voltage do not

cause any problem (see Figure 55). In this context, please note that

the high breakdown voltage of the input FETs eliminates the need

to include clamp diodes between the inputs of the amplifier, a prac-

tice that is mandatory on many precision op amps. Unfortunately,

clamp diodes greatly interfere with many application circuits

such as precision rectifiers and comparators. The AD8610/

AD8620 are free from these limitations.

V1

14V

0

+13V

3

7

6

2

4 AD8610

–13V

Figure 56. Unity Gain Follower

No Phase Reversal

Many amplifiers misbehave when one or both of the inputs are

forced beyond the input common-mode voltage range. Phase

reversal is typified by the transfer function of the amplifier, effect-

tively reversing its transfer polarity. In some cases, this can cause

lockup and even equipment damage in servo systems, and can

cause permanent damage or no recoverable parameter shifts to

the amplifier itself. Many amplifiers feature compensation cir-

cuitry to combat these effects, but some are only effective for

the inverting input. The AD8610/AD8620 are designed to prevent

phase reversal when one or both inputs are forced beyond their

input common-mode voltage range.

VIN

CH2 = 19.4V p-p

0V

TIME (400ns/DIV)

Figure 55. AD8610 FPBW

Rev. E | Page 16 of 24

VOUT

TIME (400µs/DIV)

Figure 57. No Phase Reversal

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