ICL7650BCSA - Maxim Integrated Products, Inc.

General Description

Maxim’s ICL7650/ICL7653 are chopper-stabilized

amplifiers, ideal for low-level signal processing applica-

tions. Featuring high performance and versatility, these

devices combine low input offset voltage, low input bias

current, wide bandwidth, and exceptionally low drift

over time and temperature. Low offset is achieved

through a nulling scheme that provides continuous

error correction. A nulling amplifier alternately nulls

itself and the main amplifier. The result is an input offset

voltage that is held to a minimum over the entire operat-

ing temperature range.

The ICL7650B/ICL7653B are exact replacements for

Intersil’s ICL7650B/ICL7653B. These devices have a

10µV max offset voltage, a 0.1µV/°C max input offset

voltage temperature coefficient, and a 20pA max bias

current—all specified over the commercial temperature

range.

A 14-pin version is available that can be used with

either an internal or external clock. The 14-pin version

has an output voltage clamp circuit to minimize over-

load recovery time.

Applications

Condition Amplifier

Precision Amplifier

Instrumentation Amplifier

Thermocouples

Thermistors

Strain Gauges

Features

♦ICL7650/53 are Improved Second Sources to

ICL7650B/53B

♦Lower Supply Current: 2mA

♦Low Offset Voltage: 1µV

♦No Offset Voltage Trimming Needed

♦High-Gain CMRR and PSRR: 120dB min

♦Lower Offset Drift with Time and Temperature

♦Extended Common-Mode Voltage Range

♦Low DC Input Bias Current: 10pA

♦Monolithic, Low-Power CMOS Design

ICL7650/ICL7650B/ICL7653/ICL7653B

Chopper-Stabilized Op Amps

________________________________________________________________ Maxim Integrated Products 1

ICL7650

ICL7653

OUTPUT

INVERTING AMPLIFIER

WITH OPTIONAL CLAMP

INPUT

CLAMP

Typical Operating Circuit

19-0960; Rev 2; 1/00

Pin Configurations appear at end of data sheet.

Ordering Information

PART

ICL7650CSA

ICL7650CSD

ICL7650CPA 0°C to +70°C

0°C to +70°C

TEMP. RANGE PIN-PACKAGE

8 SO

14 SO

8 Plastic DIP

ICL7650CPD

ICL7650CTV

ICL7650C/D 0°C to +70°C

0°C to +70°C

0°C to +70°C 14 Plastic DIP

8 TO-99

Dice

ICL7650IJA

ICL7650IJD -20°C to +85°C

-20°C to +85°C 8 CERDIP

14 CERDIP

ICL7650MTV

ICL7650MJD -55°C to +125°C

-55°C to +125°C 8 CERDIP

14 CERDIP

ICL7650BCSA

ICL7650BCSD 0°C to +70°C

0°C to +70°C 8 SO

14 SO

ICL7650BCPA

ICL7650BCPD 0°C to +70°C

0°C to +70°C 8 Plastic DIP

14 Plastic DIP

ICL7650BCTV

ICL7650BC/D 0°C to +70°C

0°C to +70°C 8 TO-99

Dice

ICL7653CSA

ICL7653CPA

ICL7653CTV

0°C to +70°C 8 SO

ICL7653BCSA

ICL7653BCPA

0°C to +70°C

0°C to +70°C 8 Plastic DIP

8 TO-99

0°C to +70°C

ICL7653IJA

ICL7653MTV -55°C to +125°C

-20°C to +85°C 8 CERDIP

8 CERDIP

0°C to +70°C 8 SO

8 Plastic DIP

ICL7653BCTV 0°C to +70°C 8 TO-99

For free samples and the latest literature, visit www.maxim-ic.com or phone 1-800-998-8800.

For small orders, phone 1-800-835-8769.

ICL7650/ICL7650B/ICL7653/ICL7653B

Chopper-Stabilized Op Amps

2 _______________________________________________________________________________________

ABSOLUTE MAXIMUM RATINGS

ELECTRICAL CHARACTERISTICS—ICL7650B/ICL7653B

(Circuit of Figure 1, V+ = +5V, V- = -5V, TA= +25°C, unless otherwise noted.)

Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional

operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to

absolute maximum rating conditions for extended periods may affect device reliability.

Total Supply Voltage (V+ to V-)..............................................18V

Input Voltage ........................................(V+ + 0.3V) to (V- - 0.3V)

Voltage on Oscillator Control Pins

(except EXT/CLOCK IN).............................................V+ to V-

Voltage on EXT/CLOCK IN ..................(V+ + 0.3V) to (V+ - 6.0V)

Duration of Output Short Circuit ....................................Indefinite

Current into Any Pin ............................................................10mA

Current into Any Pin while Operating (Note 1)...................100µA

Continuous Total Power Dissipation (TA= +70°C)

8-Pin SO (derate 5.88mW/°C above +70°C)...............471mW

8-Pin PDIP (derate 6.9mW/°C above +70°C)...............552mW

8-Pin CERDIP (derate 8.0mW/°C above +70°C).........640mW

8-Pin TO-99 (derate 6.7mW/°C above +70°C)............533mW

14-Pin SO (derate 8.3mW/°C above +70°C)...............667mW

14-Pin PDIP (derate 10.0mW/°C above +70°C)..........800mW

14-Pin CERDIP (derate 9.1mW/°C above +70°C).......727mW

Operating Temperature Ranges

ICL765_C_ _/ICL755_BC_ _ ...............................0°C to +70°C

ICL765_I__/ICL755_BI__................................-20°C to +85°C

ICL765_M__/ICL755_BM__..........................-55°C to +125°C

Storage Temperature Range .............................-65°C to +150°C

Junction Temperature......................................................+150°C

Lead Temperature (soldering, 10s) .................................+300°C

CL= 50pF, RL= 10kΩ

f = 10Hz

RS= 100Ω, f = 0 to 10Hz

V+ to V- = ±3V to ±8V

CMVR = -5V to +1.6V

RL= 100kΩ

RL= 10kΩ

Doubles every 10°

-20°C < TA< +85°C

TA= +25°C

-55°C < TA< +85°C

-55°C < TA< +125°C

TA= +25°C

CONDITIONS

µs0.2tr

Rise Time

V/µs2.5SRSlew Rate

MHz2.0GBWUnity-Gain Bandwidth

pA/√Hz

0.01In

Input Noise Current

µVp-p2enp-p

Input Noise Voltage

dB120 130PSRRPower-Supply Rejection Ratio

dB120 130CMRRCommon-Mode Rejection Ratio

V-5.0 -5.2 to +2.0 1.6CMVRCommon-Mode Voltage Range

±4.95 V

±4.7 ±4.85

VOUT

Output Voltage Swing (Note 3)

V/V

1 ·1055 ·108

AVOL

Large-Signal Voltage Gain

Ω

1012

RIN

Input Resistance

pA0.5IOS

Input Offset Current (Note 2)

100

35 pA

1.5 10

IBIAS

Input Bias Current

0.01 0.05

µV

±0.7 ±5

VOS

Input Offset Voltage ±10

5.0

µV/°C

∆VOS

∆T

Average Temperature Coefficient

of Input Offset Voltage

UNITSMIN TYP MAXSYMBOLPARAMETER

Note 1: Maxim recommends limiting the input current to 100µA to avoid latchup problems. A value of 1mA is typically safe; however,

this is not guaranteed.

TA= +25°C

0°C < TA< +70°C

-20°C < TA< +85°C

%20Overshoot

V4.5 16V+ to V-Operating Supply Range

No load mA2.0 3.5ISUPP

Supply Current

ICL7650/ICL7650B/ICL7653/ICL7653B

Chopper-Stabilized Op Amps

_______________________________________________________________________________________ 3

ELECTRICAL CHARACTERISTICS—ICL7650/ICL7653

(Circuit of Figure 1, V+ = +5V, V- = -5V, TA= +25°C, unless otherwise noted.) (Note 5)

ELECTRICAL CHARACTERISTICS—ICL7650B/ICL7653B (continued)

(Circuit of Figure 1, V+ = +5V, V- = -5V, TA= +25°C, unless otherwise noted.)

Note 2: IOS = 2 ·IBIAS

Note 3: OUTPUT and CLAMP pins not connected.

Note 4: See Output Clamp section for details.

CONDITIONS UNITSMIN TYP MAXSYMBOLPARAMETER

-4.0V < VOUT < +4.0V pA1Clamp Off Current (Note 4)

No load nV/

√month

100Offset Voltage vs. Time

0°C ≤TA≤+70°C

-20°C ≤TA≤+85°C

-55°C ≤TA≤+125°C

0°C ≤TA≤+70°C

RL= 100kΩ

RL= 10kΩ

-55°C ≤TA≤+125°C

ICL765_

TA= +25°C

ICL765_

(Note 6)

CONDITIONS

-5.0 -5.2 to +3.0 2.5

CMVRCommon-Mode Voltage Range

±4.95 V

±4.7 ±4.85

VOUT

Output Voltage Swing (Note 3)

0.2 ·108

Ω

1012

RIN

Input Resistance

0.3 10

50 200

20 100

±10 ±50

µV

±0.7 ±5.0

VOS

Input Offset Voltage

±1.0 ±10

UNITSMIN TYP MAXSYMBOLPARAMETER

ICL765_

ICL765_B, 0°C ≤TA≤+70°C

0.01 0.1

µV/°C

0.01 0.05

∆VOS

∆T

Average Temperature Coefficient

of Input Offset Voltage (Note 6)

ICL765_

ICL765_B

0°C ≤TA≤+70°C

-20°C ≤TA≤+85°C

-55°C ≤TA≤+125°C

0.01 0.05

0.25 1.5

TA= +25°C 410

pAIB

Input Bias Current

12 20ICL765_B

ICL765_

RL= 10kΩ, TA= +25°C

V/V

1 ·1085 ·108

AVOL

Large-Signal Voltage Gain 0°C ≤TA≤+70°C 0.5 ·108

-20°C ≤TA≤+85°C 0.5 ·108

-20°C ≤TA≤+85°C -5.0 -5.2 to +3.0 2.5

-55°C ≤TA≤+125°C -4.5 -4.0 to +3.0 2.5

0°C ≤TA≤+70°C

-20°C ≤TA≤+85°C

-55°C ≤TA≤+85°C

+85°C ≤TA≤+125°C

RL= 100kΩµA25 70 200Clamp On Current (Note 4)

Pins 12–14 open (DIP) Hz120 200 375fch

Internal Chopping Frequency

-30

-10

-20

2684 10121416

MAXIMUM OUTPUT CURRENT

vs. SUPPLY VOLTAGE

ICL7650toc01

TOTAL SUPPLY VOLTAGE (V)

MAXIMUM OUTPUT CURRENT (mA)

SOURCE CURRENT

SINK CURRENT

100

0.1

25 7550 100 125 150

CLOCK RIPPLE REFERRED TO INPUT

vs. TEMPERATURE

ICL7650toc02

TEMPERATURE (°C)

CLOCK RIPPLE (µVp-p)

BROADBAND

NOISE

(AV = 1000)

0.1µF

1µF

48106 121416

SUPPLY CURRENT

vs. SUPPLY VOLTAGE

ICL7650toc03

TOTAL SUPPLY VOLTAGE (V)

SUPPLY CURRENT (mA)

Typical Operating Characteristics

(Circuit of Figure 1, V+ = +5V, V- = -5V, TA = +25°C, unless otherwise noted.)

ICL7650/ICL7650B/ICL7653/ICL7653B

Chopper-Stabilized Op Amps

4 _______________________________________________________________________________________

ELECTRICAL CHARACTERISTICS—ICL7650/ICL7653 (continued)

(Circuit of Figure 1, V+ = +5V, V- = -5V, TA= +25°C, unless otherwise noted.) (Note 5)

CL= 50pF, RL= 10kΩ

f = 10Hz

RS= 100Ω, f = 0 to 10Hz

V+ to V- = ±3V to ±8V

CMVR = -5V to +2.5V

CONDITIONS

µs0.2tr

Rise Time

V/µs2.5SRSlew Rate

MHz2.0GBWUnity-Gain Bandwidth

pA/√Hz

0.01In

Input Noise Current

µVp-p2enp-p

Input Noise Voltage

dB120 130PSRRPower-Supply Rejection Ratio

dB120 130CMRRCommon-Mode Rejection Ratio

20Overshoot

V4.5 16V+ to V-Operating Supply Range

No load mA1.2 2.0ISUPP

Supply Current

UNITSMIN TYP MAXSYMBOLPARAMETER

Pins 13 and 14 open (DIP) Hz120 200 375fCLKOUT

Internal Chopping Frequency

RL= 100kΩµA25 70 200Clamp On Current (Note 4)

-4.0 ≤VOUT ≤+4.0V pA1Clamp Off Current (Note 4)

nV/

√month

100Offset Voltage vs. Time

Note 3: OUTPUT and CLAMP pins not connected.

Note 4: See Output Clamp section for details.

Note 5: All pins are designed to withstand electrostatic discharge (ESD) levels in excess of 2000V (MIL STD 8838 Method 3015.1

test circuit).

Note 6: Sample tested. Limits are not used to calculate outgoing quality level.

ICL7650/ICL7650B/ICL7653/ICL7653B

Chopper-Stabilized Op Amps

_______________________________________________________________________________________ 5

-50 25 50-25 0 75 100 125

SUPPLY CURRENT vs.

AMBIENT TEMPERATURE

ICL7650toc04

AMBIENT TEMPERATURE (°C)

SUPPLY CURRENT (mA)

0231 45678

COMMON-MODE INPUT VOLTAGE RANGE

vs. SUPPLY VOLTAGE

ICL7650toc05

SUPPLY VOLTAGE (V)

COMMON-MODE INPUT VOLTAGE RANGE (V)

POSITIVE LIMIT

NEGATIVE LIMIT

-2

-6

-4

-8

-10

10 100 1k 10k

INPUT OFFSET VOLTAGE

vs. CHOPPING FREQUENCY

ICL7650toc06

CHOPPING FREQUENCY (CLOCK OUT) (Hz)

OFFSET VOLTAGE (µV)

-1

-2

-3

48106 121416

INPUT OFFSET VOLTAGE CHANGE

vs. SUPPLY VOLTAGE

ICL7650toc07

TOTAL SUPPLY VOLTAGE (V)

INPUT OFFSET VOLTAGE CHANGE (µV)

10 100 1k 10k

10Hzp-p NOISE VOLTAGE

vs. CHOPPING FREQUENCY

ICL7650toc08

CHOPPING FREQUENCY (CLOCK-OUT) (Hz)

DC TO 10Hz P-P NOISE VOLTAGE (µV)

100

140

120

160

0.01 1 100.1 100 1k 10k 100k

OPEN-LOOP GAIN AND PHASE SHIFT

vs. FREQUENCY

ICL7650toac09

FREQUENCY (Hz)

OPEN-LOOP GAIN (dB)

110

130

PHASE SHIFT (DEGREES)

RL = 10kΩ

CEXT = 0.1µF

100

140

120

160

0.01 1 100.1 100 1k 10k 100k

OPEN-LOOP GAIN AND PHASE SHIFT

vs. FREQUENCY

ICL7650toac10

FREQUENCY (Hz)

OPEN-LOOP GAIN (dB)

110

130

PHASE SHIFT (DEGREES)

RL = 10kΩ

CEXT = 1.0µF

-3

-2

-1

-1.0 0-0.5 0.5 1.0 1.5 2.0 2.5 3.0

VOLTAGE FOLLOWER LARGE-SIGNAL

PULSE RESPONSE

ICL7650toc11

TIME (µs)

OUTPUT VOLTAGE (V)

CLOCK OUT HIGH

CLOCK OUT LOW

-3

-2

-1

-1.0 0-0.5 0.5 1.0 1.5 2.0 2.5 3.0

VOLTAGE FOLLOWER LARGE-SIGNAL

PULSE RESPONSE

ICL7650toc12

TIME (µs)

OUTPUT VOLTAGE (V)

CLOCK OUT HIGH

CLOCK OUT LOW

Typical Operating Characteristics (continued)

(Circuit of Figure 1, V+ = +5V, V- = -5V, TA = +25°C, unless otherwise noted.)

ICL7650/ICL7650B/ICL7653/ICL7653B

Chopper-Stabilized Op Amps

6 _______________________________________________________________________________________

Detailed Description

Figure 2 shows the major elements of the ICL7650/

ICL7653. Two amplifiers are illustrated, the main amplifi-

er and the nulling amplifier, both of which have offset-

null capability. The main amplifier is connected full time

from the input to the output. The nulling amplifier, under

control of the chopper-frequency oscillator and clock

circuit, alternately nulls itself and the main amplifier. This

nulling arrangement, which is independent of the output

level, operates over the full power-supply and common-

mode ranges. The ICL7650/ICL7653 exhibit an excep-

tionally high CMRR, PSRR, and AVOL. Their nulling

connections, which are MOSFET back gates, have inher-

ently high impedance. Two external capacitors provide

storage for the nulling potentials and the necessary

nulling-loop time constants.

The ICL7650/ICL7653 minimize chopper-frequency

charge injection at the input terminals by carefully bal-

ancing the input switches. Feed-forward injection into

the compensation capacitor, the main cause of output

spikes in this type of circuit, is also minimized.

Output Clamp (ICL7650 Only)

The output clamp reduces the overload recovery time

inherent with chopper-stabilized amplifiers. When tied to

the summing junction or inverting input pin, a current path

between this point and the output occurs just before the

output device saturates. This prevents uncontrolled input

differential and the consequent charge build-up on the

correction-storage capacitors, while causing only a slight

reduction in the output swing.

Intermodulation

Intermodulation effects can cause problems in older

chopper-stabilized amplifier modules. Intermodulation

occurs since the amplifier has a finite AC gain, and

therefore will have a small AC signal at the input. In a

chopper-stabilized module, this small AC signal is

detected, chopped, and fed into the offset-correction

circuit. This results in spurious outputs at the sum and

difference frequencies of the chopping and input signal

frequencies. Other intermodulation effects in chopper-

stabilized modules include gain and phase anomalies

near the chopping frequency.

These effects are substantially reduced in the

ICL7650/ICL7653, which add to the nulling circuit a

dynamic current that compensates for the AC signal on

the inputs. Unlike modules, the ICL7650/ICL7653 can

precisely compensate for the finite AC gain, since both

the AC gain rolloff and the intermodulation compensation

current are controlled by internal matched capacitors.

ICL7650

ICL7653

OUTPUT

0.1µF 0.1µF

ICL7650

INTERNAL

BIAS

EXT CLK IN

CLK OUT

NULL

CEXTA CEXTB

CAP RETURN

OUTPUT

+IN

-IN CLAMP

MAIN

INT/EXT

A = CLK OUT

EXT CLK IN

OSC

Figure 1. ICL7650 Test Circuit

Figure 2. Block Diagram

ICL7650/ICL7650B/ICL7653/ICL7653B

Chopper-Stabilized Op Amps

_______________________________________________________________________________________ 7

Nulling Capacitor Connection

Separate pins are provided for CRETN and CLAMP in

the ICL7650. If you do not need the clamp feature,

order the ICL7653; this device only offers the CRETN pin

and will produce slightly lower noise and improved AC

common-mode rejection. If you need to use the clamp

feature, order the ICL7650 and connect the external

capacitors to V-. To prevent load-current IR drops and

other extraneous signals from being injected into the

capacitors, use a separate PC board trace to connect

the capacitor commons directly to the V- pin. The out-

side foil of the capacitors should be connected to the

low-impedance side of the null storage circuit, V- or

CRETN. This will act as an ESD voltage shield.

Clock Operation

The ICL7650’s internal oscillator generates a 200Hz fre-

quency, which is available at the CLK OUT pin. The

device can also be operated with an external clock, if

desired. An internal pull-up permits the INT/EXT pin to

be left open for normal operation. However, the internal

clock must be disabled and INT/EXT must be tied to V-

if an external clock is used. An external clock signal

may then be applied to the EXT CLK IN pin. The duty

cycle of the external clock is not critical at low frequen-

cies. However, a 50% to 80% positive duty cycle is pre-

ferred for frequencies above 500Hz, since the

capacitors are charged only when EXT CLK IN is high.

This ensures that any transients have time to settle

before the capacitors are turned off. The external clock

should swing between ground and V+ for power sup-

plies up to ±6V, and between V+ and (V+ - 6V) for

higher supply voltages.

To avoid a capacitor imbalance during overload, use a

strobe signal. Neither capacitor will be charged if a

strobe signal is connected to EXT CLK IN so that it is

low while the overload signal is being applied to the

amplifier. A typical amplifier will drift less than 10µVs

since the leakage of the capacitor pins is quite low at

room temperature. Relatively long measurements may

be made with little change in offset.

Applications Information

Device Selection

In applications that require lowest noise, Maxim’s

ICL7652 may be preferred over the ICL7650/ICL7653.

The ICL7650/ICL7653 offer a higher gain-bandwidth

product and lower input bias currents, while the

ICL7652 reduces noise by using larger input FETs.

These larger FETs, however, increase the leakage at

the ICL7652’s external null pins. Therefore, the

ICL7650/ICL7653 can operate to a higher temperature

with 0.1µF capacitors before the clock ripple (due to

leakage at the null capacitor pins) becomes excessive

and 1µF external capacitors are required.

Output Stage/Load Driving

The ICL7650/ICL7653 somewhat resemble a transcon-

ductance amplifier whose open-loop gain is proportional

to load resistance. This behavior is apparent when loads

are less than the high-impedance stage (approximately

18kΩfor one output circuit). The open-loop gain, for

example, will be 17dB lower with a 1kΩload than with a

10kΩload. This lower gain is of little consequence if the

amplifier is used strictly for DC since the DC gain is typi-

cally greater than 120dB, even with a 1kΩload. For

wideband applications, however, the best frequency

response will be achieved with a load resistor of 10kΩor

higher. The result will be a smooth 6dB per octave

response from 0.1Hz to 2MHz, with phase shifts of less

than 10° in the transition region where the main amplifier

takes over from the null amplifier.

Component Selection

CEXTA and CEXTB, the two required capacitors, have

optimum values depending on the clock or chopping

frequency. The correct value is 0.1µF for the preset

internal clock. When using an external clock, scale this

component value in proportion to the relationship

between the chopping frequency and the nulling time

constant. A low-leakage ceramic capacitor may prove

suitable for many applications; however, a high-quality

film-type capacitor (such as mylar) is preferred. For

lowest settling time at initial turn-on, use capacitors with

low dielectric absorption (such as polypropylene

types). With low-dielectric-absorption capacitors, the

ICL7650/ICL7653 will settle to 1µV offset in 100ms, but

several seconds may be required if ceramic capacitors

are used.

Thermoelectric Effects

Thermoelectric effects developed in thermocouple

junctions of dissimilar materials (metals, alloys, silicon,

etc.) ultimately limit precision DC measurements.

Unless all junctions are at the same temperature, ther-

moelectric voltages (typically around 10µV/°C, but up

to hundreds of µV/°C for some materials) will be gener-

ated. In order to realize the extremely low offset volt-

ages that the chopper amplifier can provide, take

special precautions to avoid temperature gradients. To

eliminate air movement, enclose all components (par-

ticularly those caused by power-dissipating elements in

the system). Minimize power-supply voltages and

power dissipation, and use low-thermoelectric-coeffi-

cient connections where possible. It is advisable to

separate the device surrounding heat-dissipating ele-

ments, and to use high-impedance loads.

ICL7650/ICL7650B/ICL7653/ICL7653B

Chopper-Stabilized Op Amps

8 _______________________________________________________________________________________

Input Guarding

Low-leakage, high-impedance CMOS inputs allow the

ICL7650/ICL7653 to measure high-impedance sources.

Stray leakage paths can decrease input resistance and

increase input currents unless inputs are guarded.

Boards must be thoroughly cleaned with TCE or alcohol

and blown dry with compressed air. The board should

be coated with epoxy or silicone after cleaning to pre-

vent contamination.

Leakage currents may cause trouble even with properly

cleaned and coated boards, particularly since the input

pins are adjacent to pins that are at supply potentials.

Leakage can be significantly reduced by using guard-

ing to decrease the voltage difference between inputs

and adjacent metal runs. Use a 10-lead pin circle, with

the leads of the device formed so that the holes adja-

cent to the inputs are empty when it is inserted in the

board to accomplish input guarding of the 8-pin TO-99

package. A conductive ring surrounding the inputs, the

“guard,” is connected to a low-impedance point that is

approximately the same voltage as the inputs. The

guard then absorbs the leakage current from the high-

voltage pins. Typical guard connections are shown in

Figure 3.

OUTPUT

INVERTING AMPLIFIER FOLLOWER

INPUT R2

R3*

OUTPUT

INPUT

USE R3 TO COMPENSATE FOR LARGE

SOURCE RESISTANCES, OR FOR CLAMP

OPERATION (FIGURE 5).

NONINVERTING AMPLIFIER

R3*

OUTPUT

INPUT

NOTE: SHOULD BE LOW IMPEDANCE FOR

OPTIMUM GUARDING.

R1 R2

R1 + R2

BOTTOM VIEW

BOARD LAYOUT FOR INPUT GUARDING

WITH TO-99 PACKAGE.

V+

V-

GUARD

INPUTS

OUTPUT

EXTERNAL

CAPACITORS

EXTERNAL

CAPACITORS

543

Figure 3. Input Guard Connection

The 14-pin DIP configuration has been specifically

designed to ease input guarding. The pins adjacent to

the inputs are not used.

Pin Compatibility

The ICL7653’s pinout generally corresponds to that of

industry-standard 8-pin devices such as the LM741 or

LM101. However, its external null storage capacitors

are connected to pins 1 and 8; whereas most op amps

leave these pins open or use them for offset null or

compensation capacitors.

The OP05 and OP07 op amps can be converted for

ICL7650/ICL7653 operation. This can be accomplished

by removing the offset null potentiometer, which is con-

nected from pins 1 and 8 to V+, and replacing it with

two capacitors connected from pins 1 and 8 to V-. For

LM108 devices, the compensation capacitor is

replaced by the external nulling capacitors. Pin 5 is the

output clamp connection on the ICL7650/ICL7653. By

removing any circuit connections from this pin, the

LM101/LM748/LM709 devices can undergo a similar

conversion.

Typical Applications

Figure 4 shows the ICL7650/ICL7653 automatically

nulling the offset voltage of a high-speed amplifier. The

ICL7650/ICL7653 continuously monitor the voltage at

the amplifier’s inverting input, integrate the error, and

drive the amplifier’s noninverting input to correct for the

offset voltage detected at the inverting input. The cir-

cuit’s DC offset characteristics are determined by the

ICL7650/ICL7653, and its AC performance is deter-

mined by the high-speed amplifier. While this circuit

continuously and automatically adjusts the amplifier’s

offset to less than 5µV, it does not correct for errors

caused by the input bias current, so the value of resis-

tor RFshould be as low as is practical. This technique

can be used with any op amp that is configured as an

inverting amplifier.

Figures 5 and 6 illustrate basic inverting and noninvert-

ing amplifier circuits. Both figures show an output

clamping circuit being used to enhance overload

recovery performance. Supply voltage (±8V max) and

output drive capability (10kΩload for full swing) are the

only limitations to consider when replacing other op

amps with the ICL7650/ICL7653. Use a simple booster

circuit to overcome these limitations (Figure 7). This

enables the full output capabilities of the LM118 (or any

other standard device) to be combined with the input

capabilities of the ICL7650/ICL7653. Observe the loop

gain stability carefully when the feedback network is

added, particularly when a slower amplifier such as the

LM741 is used.

A lower voltage supply is required when mixing the

ICL7650/ICL7653 with circuits that operate at ±15V sup-

plies. One approach is to use a highly efficient voltage

divider. This is illustrated in Figure 8, where the ICL7660

voltage converter is used to convert +15V to +7.5V.

ICL7650/ICL7650B/ICL7653/ICL7653B

Chopper-Stabilized Op Amps

_______________________________________________________________________________________ 9

HIGH-

SPEED

AMP

0.1µF

47Ω 10k

100k

ICL7650

ICL7653

VOUT

RIN

ICL7650

OUTPUT

(R1 || R2) ≥ 100kΩ

FOR FULL CLAMP EFFECT

INPUT

CLAMP

0.1µF 0.1µF

NOTE: R1 || R2 INDICATES THE

PARALLEL COMBINATION OF

R1 || R2.

Figure 4. Nulling a High-Speed Amplifier

Figure 5. Inverting Amplifier with Optional Clamp

ICL7650/ICL7650B/ICL7653/ICL7653B

Chopper-Stabilized Op Amps

10 ______________________________________________________________________________________

-INPUT

+INPUT

V-

CEXTA

CEXTB EXT/CLK IN

INT/EXT

INT/

CLK OUT

V+

OUTPUT

CLAMP

CRETN

0.069"

(1.75mm)

0.090"

(2.29mm)

ICL7660

10µF

+15V

+7.5V

Chip Topography

Figure 8. Splitting +15V with an ICL7660, 95% Efficiency

(Same for -15V)

ICL7650

OUTPUT

INPUT

CLAMP

0.1µF 0.1µF

NOTE: R1 || R2 INDICATES THE

PARALLEL COMBINATION OF

R1 || R2.

R3 + (R1 || R2) > 100kΩ

FOR FULL CLAMP EFFECT

ICL7650

CLAMP

0.1µF

-7.5V

-15V

10k

+15V

+7.5V

0.1µF

741

OUT

Figure 6. Noninverting Amplifier with Optional Clamp

Figure 7. Using an Industry-Standard 741 to Boost Output

Drive Capability

ICL7650/ICL7650B/ICL7653/ICL7653B

Chopper-Stabilized Op Amps

______________________________________________________________________________________ 11

TOP VIEW

OUTPUT

CRETN

V-

CEXTB

V+-INPUT

+INPUT

CEXTA

ICL7653

OUTPUT

CLAMPV-

CEXTB

V+-INPUT

+INPUT

CEXTA

ICL7650

OUTPUT-INPUT

CRETN

V+

+INPUT

CEXTA

CEXTB

V-

1 7

ICL7653

OUTPUT-INPUT

CLAMP

V+

+INPUT

CEXTA

CEXTB

V-

1 7

ICL7650

INT/EXT

EXT/CLK IN

INT/CLK OUT

V+-INPUT

N.C. (GUARD)

CEXTA

CEXTB

MAX7650

OUTPUT

CLAMP

CRETN

V-

N.C. (GUARD)

+INPUT

N.C. = NO INTERNAL CONNECTION

SO/DIP/CERDIP

SO/DIP/CERDIP TO-99

TO-99

Pin Configurations

ICL7650/ICL7650B/ICL7653/ICL7653B

Chopper-Stabilized Op Amps

Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are

implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.

12 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600

Package Information

SOICN.EPS