Datasheet ICL7650BCD, ICL7650BCPA, ICL7650BCPD, ICL7650BCSA, ICL7650BCSD Datasheet (Maxim Integrated Producs)

General Description

Maxim’s ICL7650/ICL7653 are chopper-stabilized
amplifiers, ideal for low-level signal processing applica­tions. 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 operat­ing 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 over­load 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

C

R

C

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

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 [phone].
For small orders, phone [phone].

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 (T

A

= +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

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

TA= +25°C

CONDITIONS

µs0.2t

r

Rise Time

V/µs2.5SRSlew Rate

MHz2.0GBWUnity-Gain Bandwidth

pA/√Hz

0.01I

n

Input Noise Current

µVp-p2e

np-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

V

OUT

Output Voltage Swing (Note 3)

V/V

1 · 1055 · 10

8

A

VOL

Large-Signal Voltage Gain

Ω

10

12

R

IN

Input Resistance

pA0.5I

OS

Input Offset Current (Note 2)

100

35

pA

1.5 10

I

BIAS

Input Bias Current

0.01 0.05

µV

±0.7 ±5

V

OS

Input Offset Voltage

±10

5.0

µV/°C

50

∆V

OS

∆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 3.5I

SUPP

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: I

OS

= 2 · I

BIAS

Note 3: OUTPUT and CLAMP pins not connected.
Note 4: See Output Clamp section for details.

CONDITIONS UNITSMIN TYP MAXSYMBOLPARAMETER

-4.0V < V

OUT

< +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

V

-5.0 -5.2 to +3.0 2.5

CMVRCommon-Mode Voltage Range

±4.95

V

±4.7 ±4.85

V

OUT

Output Voltage Swing (Note 3)

0.2 · 10

8

Ω

10

12

R

IN

Input Resistance

0.3 10

50 200

20 100

±10 ±50

µV

±0.7 ±5.0

V

OS

Input Offset Voltage

±1.0 ±10

±1.0 ±10

±1.0 ±10

UNITSMIN TYP MAXSYMBOLPARAMETER

ICL765_

ICL765_B, 0°C ≤ TA≤ +70°C

0.01 0.1

µV/°C

0.01 0.05

∆V

OS

∆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

0.01 0.05

0.25 1.5

TA= +25°C

410

pAI

B

Input Bias Current

12 20ICL765_B

ICL765_

RL= 10kΩ, TA= +25°C

V/V

1 · 1085 · 10

8

A

VOL

Large-Signal Voltage Gain

0°C ≤ TA≤ +70°C

0.5 · 10

8

-20°C ≤ TA≤ +85°C

0.5 · 10

8

-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= 100kΩ µA25 70 200Clamp On Current (Note 4)

Pins 12–14 open (DIP) Hz120 200 375f

ch

Internal Chopping Frequency

-30

-10

-20

1

0

3

2

4

2684 10121416

MAXIMUM OUTPUT CURRENT

vs. SUPPLY VOLTAGE

ICL7650toc01

TOTAL SUPPLY VOLTAGE (V)

MAXIMUM OUTPUT CURRENT (mA)

SOURCE CURRENT

SINK CURRENT

1k

100

10

1

0.1
25 7550 100 125 150

CLOCK RIPPLE REFERRED TO INPUT

vs. TEMPERATURE

ICL7650toc02

TEMPERATURE (°C)

CLOCK RIPPLE (µVp-p)

BROADBAND

NOISE

(A

V

= 1000)

0.1µF

1µF

0

1

2

3

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

µs0.2t

r

Rise Time

V/µs2.5SRSlew Rate

MHz2.0GBWUnity-Gain Bandwidth

pA/√Hz

0.01I

n

Input Noise Current

µVp-p2e

np-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 2.0I

SUPP

Supply Current

UNITSMIN TYP MAXSYMBOLPARAMETER

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

CLKOUT

Internal Chopping Frequency

RL= 100kΩ µA25 70 200Clamp On Current (Note 4)

-4.0 ≤ V

OUT

≤ +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

0

1

2

3

-50 25 50-25 0 75 100 125

SUPPLY CURRENT vs.

AMBIENT TEMPERATURE

ICL7650toc04

AMBIENT TEMPERATURE (°C)

SUPPLY CURRENT (mA)

0

2

1

4

3

5

6

7

8

0231 45678

COMMON-MODE INPUT VOLTAGE RANGE

vs. SUPPLY VOLTAGE

ICL7650toc05

SUPPLY VOLTAGE (V)

COMMON-MODE INPUT VOLTAGE RANGE (V)

POSITIVE LIMIT

NEGATIVE LIMIT

0

-2

-6

-4

-8

-10

10 100 1k 10k

INPUT OFFSET VOLTAGE

vs. CHOPPING FREQUENCY

ICL7650toc06

CHOPPING FREQUENCY (CLOCK OUT) (Hz)

OFFSET VOLTAGE (µV)

3

1

2

-1

0

-2

-3

48106 121416

INPUT OFFSET VOLTAGE CHANGE

vs. SUPPLY VOLTAGE

ICL7650toc07

TOTAL SUPPLY VOLTAGE (V)

INPUT OFFSET VOLTAGE CHANGE (µV)

0

1

3

2

4

5

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)

20

60

40

100

80

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

70

90

50

PHASE SHIFT (DEGREES)

RL = 10kΩ
C

EXT

= 0.1µF

20

60

40

100

80

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

70

90

50

PHASE SHIFT (DEGREES)

RL = 10kΩ
C

EXT

= 1.0µF

-3

-2

-1

0

1

2

3

-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

0

1

2

3

-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 amplifi­er and the nulling amplifier, both of which have offset­null 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 common­mode ranges. The ICL7650/ICL7653 exhibit an excep­tionally high CMRR, PSRR, and A

VOL

. Their nulling
connections, which are MOSFET back gates, have inher­ently 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 bal­ancing 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 chopper­stabilized 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

C

C

R

C

0.1µF 0.1µF

R2

1M

R1

1M

ICL7650

INTERNAL

BIAS

EXT CLK IN

CLK OUT

NULL

C

EXTA

C

EXTB

CAP RETURN

B

A

C

P

A

+

-

N

OUTPUT

+IN

-IN

CLAMP

MAIN

+

-

B
C

INT/EXT

A

A

A = CLK OUT

A

EXT CLK IN

B

C

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 C

RETN

and CLAMP in
the ICL7650. If you do not need the clamp feature,
order the ICL7653; this device only offers the C

RETN

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 out­side foil of the capacitors should be connected to the
low-impedance side of the null storage circuit, V- or
C

RETN

. This will act as an ESD voltage shield.

Clock Operation

The ICL7650’s internal oscillator generates a 200Hz fre­quency, 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 frequen­cies. However, a 50% to 80% positive duty cycle is pre­ferred 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 sup­plies 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 transcon­ductance amplifier whose open-loop gain is proportional
to load resistance. This behavior is apparent when loads
are less than the high-impedance stage (approximately
18kΩ for one output circuit). The open-loop gain, for
example, will be 17dB lower with a 1kΩ load than with a
10kΩ load. This lower gain is of little consequence if the
amplifier is used strictly for DC since the DC gain is typi­cally greater than 120dB, even with a 1kΩ load. For
wideband applications, however, the best frequency
response will be achieved with a load resistor of 10kΩ or
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

C

EXTA

and C

EXTB

, 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, ther­moelectric voltages (typically around 10µV/°C, but up
to hundreds of µV/°C for some materials) will be gener­ated. In order to realize the extremely low offset volt­ages that the chopper amplifier can provide, take
special precautions to avoid temperature gradients. To
eliminate air movement, enclose all components (par­ticularly those caused by power-dissipating elements in
the system). Minimize power-supply voltages and
power dissipation, and use low-thermoelectric-coeffi­cient connections where possible. It is advisable to
separate the device surrounding heat-dissipating ele­ments, 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 pre­vent 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 adja­cent 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 high­voltage pins. Typical guard connections are shown in
Figure 3.

OUTPUT

INVERTING AMPLIFIER

FOLLOWER

INPUT

R2

R1

R3*

R3*

OUTPUT

INPUT

USE R3 TO COMPENSATE FOR LARGE
SOURCE RESISTANCES, OR FOR CLAMP
OPERATION (FIGURE 5).

*

NONINVERTING AMPLIFIER

R3*

OUTPUT

INPUT

R2

R1

NOTE:

SHOULD BE LOW IMPEDANCE FOR
OPTIMUM GUARDING.

R1 R2

R1 + R2

BOTTOM VIEW

BOARD LAYOUT FOR INPUT GUARDING
WITH TO-99 PACKAGE.

1

V+

V-

GUARD

INPUTS

OUTPUT

EXTERNAL

CAPACITORS

EXTERNAL

CAPACITORS

87

6

5

4

3

2

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 con­nected 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 cir­cuit’s DC offset characteristics are determined by the
ICL7650/ICL7653, and its AC performance is deter­mined 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 resis­tor R

F

should 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 noninvert­ing amplifier circuits. Both figures show an output
clamping circuit being used to enhance overload
recovery performance. Supply voltage (±8V max) and
output drive capability (10kΩ load 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 sup­plies. 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

HIGH­SPEED

AMP

0.1µF

47Ω 10k

100k

R

F

ICL7650
ICL7653

V

OUT

R

IN

ICL7650

OUTPUT

(R1 || R2) ≥ 100kΩ
FOR FULL CLAMP EFFECT

INPUT

C

R

C

CLAMP

0.1µF 0.1µF

R2

R1
1k

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-

C

EXTA

C

EXTB

EXT/CLK IN

INT/EXT

INT/
CLK OUT

V+

OUTPUT

CLAMP

C

RETN

0.069"

(1.75mm)

0.090"

(2.29mm)

ICL7660

45

3

8

6

2

10µF

10µF

1M

+15V

+7.5V

0V

Chip Topography

Figure 8. Splitting +15V with an ICL7660, 95% Efficiency
(Same for -15V)

ICL7650

OUTPUT

INPUT

C

R

C

CLAMP

0.1µF 0.1µF

R3

R2

R1

NOTE: R1 || R2 INDICATES THE
PARALLEL COMBINATION OF
R1 || R2.

R3 + (R1 || R2) > 100kΩ
FOR FULL CLAMP EFFECT

ICL7650

IN

+

-

CLAMP

0.1µF

-7.5V

-15V

10k

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

C

RETN

V-

1

2

87C

EXTB

V+-INPUT

+INPUT

C

EXTA

3

4

6

5

ICL7653

OUTPUT

CLAMPV-

1

2

87C

EXTB

V+-INPUT

+INPUT

C

EXTA

3

4

6

5

ICL7650

OUTPUT-INPUT

C

RETN

V+

+INPUT

C

EXTA

C

EXTB

V-

62

8

4

5

1 7

3

ICL7653

OUTPUT-INPUT

CLAMP

V+

+INPUT

C

EXTA

C

EXTB

V-

62

8

4

5

1 7

3

ICL7650

14

13

12

11

10

9

8

1

2

3

4

5

6

7

INT/EXT

EXT/CLK IN

INT/CLK OUT

V+-INPUT

N.C. (GUARD)

C

EXTA

C

EXTB

MAX7650

OUTPUT

CLAMP

C

RETN

V-

N.C. (GUARD)

+INPUT

N.C. = NO INTERNAL CONNECTION

SO/DIP/CERDIP

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.

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© 2000 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.

Package Information

SOICN.EPS