LTC7652_15 datasheet(12/24 Pages) LINER

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LTC1052/LTC7652

1052fa

OUTPUT CLAMP

If the LTC1052 is driven into saturation, the nulling loop,

attempting to force the differential input voltage to zero,

will drive CEXTA and CEXTB to a supply rail. After the

saturating drive is removed, the capacitors take a finite

time to recover—this is the overload recovery time. The

overload recovery is longest when the capacitors are

driven to the negative rail (refer to Overload Recovery in

the Typical Performance Characteristics section). The

overload recovery time in this case is typically 225ms. In

the opposite direction (i.e., CEXTA and CEXTB at positive

rail), it is about ten times faster (25ms). The overload

recovery time for the LTC1052 is much faster than com-

petitive devices; however, if a faster overload recovery

time is necessary, the output clamp function can be used.

When the output clamp is connected to the negative input

it prevents the amplifier from saturating, thus keeping

CEXTA and CEXTB at their nominal voltages. The output

clamp is a switch that turns on when the output gets to

APPLICATIO S I FOR ATIO

within approximately 1V of either supply rail. This switch

is in parallel with the amplifier’s feedback resistor. As the

output moves closer to the rail, the switch on

resistance decreases, reducing the closed loop gain. The

output swing is reduced when the clamp function is used.

How much current the output clamp leaks when off

is important because, when used, it is connected to the

amplifier’s negative input. Any current acts like input bias

current and will degrade accuracy. At the other extreme,

the maximum current the clamp conducts when on deter-

mines how much overdrive the clamp will take, and still

keep the amplifier from saturating. Both of these numbers

are guaranteed in the Electrical Characteristics section.

LOW SUPPLY OPERATION

The minimum supply voltage for proper operation of the

LTC1052 is typically 4.0V (±2.0V). In single supply

applications, PSRR is guaranteed down to 4.7V (±2.35V).

This assures proper operation down to the minimum TTL

specified voltage of 4.75V.

TYPICAL APPLICATIO S

5V Powered Ultraprecision Instrumentation Amplifier

Fast Precision Inverter

LTC1052/7652 • TA04

8pF

–5V

1N4148

10k*

1000pF

300pF

0.1µF

*1% METAL FILM

INPUT

0.1µF

10k

–5V

OUTPUT

10k

FULL POWER BANDWIDTH = 2MHz

SLEW RATE = 40V/µs

SETTLING (10V STEP) = 12µs TO 0.01%

BIAS CURRENT DC = 30pA

OFFSET DRIFT = 50nV/°C

OFFSET VOLTAGE = 5µV

10k*

–

LT318A

–

LTC1052

LTC1052/7652 • TA03

+IN

VOUT

0.1µF

LTC1043

43k

0.22µF

100k

–IN

1N914

0.0047µF

100

≈ – 0.5V

CIRCUITRY WITHIN DASHED LINES MAY BE DELETED IF OUTPUT

DOES NOT HAVE TO SWING ALL THE WAY TO GROUND

1µF

0.1µF

10k

DRIFT = 50nV/°C

VOS = 3µV

GAIN =

CMRR = >120dB DC – 20kHz

BANDWIDTH = 10Hz

+ 1

–

LTC1052

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