File Number

2920.5

ICL7650S

2MHz, Super Chopper-Stabilized
Operational Amplifier

The ICL7650S Super Chopper-Stabilized Amplifier offers
exceptionally low input offset voltage and is extremely stable
with respect to time and temperature. It is a direct
replacement for the industry-standard ICL7650 offering
improved input offset voltage, lower input offset voltage
temperature coefficient, reduced input bias current, and
wider common mode voltage range. All improvements are
highlighted in bold italics in the Electrical Characteristics
section. Critical parameters are guaranteed over the
entire commercial temperature range.

Intersil's unique CMOS chopper-stabilized amplifier circuitry
is user-transparent, virtually eliminating the traditional
chopper amplifier problems of intermodulation effects,
chopping spikes, and overrange lockup.

The chopper amplifier achieves its low offset by comparing
the inverting and non-inverting input voltages in a nulling
amplifier, nulled by alternate clock phases. Two external
capacitors are required to store the correcting potentials on
the two amplifier nulling inputs; these are the only external
components necessary.

The clock oscillator and all the other control circuitry is
entirely self-contained. However the 14 lead version includes
a provision for the use of an external clock, if required for a
particular application. In addition, the ICL7650S is internally
compensated for unity-gain operation.

Features

· Guaranteed Max Input Offset Voltage for All Temperature

Ranges

· Low Long-Term and Temperature Drifts of Input Offset

Voltage

· Guaranteed Max Input Bias Current. . . . . . . . . . . . . .10pA

· Extremely Wide Common Mode

Voltage Range . . . . . . . . . . . . . . . . . . . . . . . +3.5V to -5V

· Reduced Supply Current . . . . . . . . . . . . . . . . . . . . . . 2mA

· Guaranteed Minimum Output Source/Sink Current

· Extremely High Gain . . . . . . . . . . . . . . . . . . . . . . . .150dB

· Extremely High CMRR and PSRR . . . . . . . . . . . . . .140dB

· High Slew Rate. . . . . . . . . . . . . . . . . . . . . . . . . . . .2.5V/

· Wide Bandwidth . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2MHz

· Unity-Gain Compensated

· Clamp Circuit to Avoid Overload Recovery Problems and

Allow Comparator Use

· Extremely Low Chopping Spikes at Input and Output

· Improved, Direct Replacement for Industry-Standard

ICL7650 and other Second-Source Parts

Pinouts

Ordering Information

PART NUMBER

TEMP.

RANGE

(

PACKAGE

PKG.

NO.

ICL7650SCPA-1

0 to 70

8 Ld PDIP

E8.3

ICL7650SCPD

0 to 70

14 Ld PDIP

E14.3

ICL7650SCBA-1

0 to 70

8 Ld SOIC

M8.15

ICL7650SCTV-1

0 to 70

8 Pin Metal Can

T8.C

ICL7650S (PDIP, SOIC)

TOP VIEW

ICL7650S (METAL CAN)

TOP VIEW

ICL7650S (PDIP)

TOP VIEW

EXTA

-IN

+IN

V-

EXTB

V+

OUTPUT

RETN

EXTB

OUTPUT

-IN

V-

EXTA

+IN

V+/CASE

RETN

EXTB

EXTA

NC (GUARD)

-IN

+IN

NC (GUARD)

V-

INT/EXT

EXT CLK IN

INT CLK OUT

V+

OUTPUT

OUT CLAMP

RETN

Data Sheet

April 2000

CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures.

1-888-INTERSIL or 321-724-7143

Intersil and Design is a trademark of Intersil Corporation.

Intersil Corporation 2000

Absolute Maximum Ratings

Thermal Information

Supply Voltage (V+ to V-). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .18V
Input Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . (V+ +0.3) to (V- -0.3)
Voltage on Oscillator Control Pins . . . . . . . . . . . . . . . . . . . . V+ to V-
Duration of Output Short Circuit. . . . . . . . . . . . . . . . . . . . . Indefinite
Current to Any Pin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10mA

While Operating (Note 1) . . . . . . . . . . . . . . . . . . . . . . . . . . .100

Operating Conditions

Temperature Range

ICL7650SC. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0

C to 70

Thermal Resistance (Typical, Note 2)

(

C/W)

(

C/W)

8 Lead PDIP Package . . . . . . . . . . . . .

120

N/A

14 Lead PDIP Package . . . . . . . . . . . .

N/A

8 Lead SOIC Package . . . . . . . . . . . . .

160

N/A

Metal Can Package . . . . . . . . . . . . . . .

160

Maximum Junction Temperature (Hermetic Package) . . . . . . . .175

Maximum Junction Temperature (Plastic Package) . . . . . . . .150

Maximum Storage Temperature Range . . . . . . . . . . -55

C to 150

Maximum Lead Temperature (Soldering 10s) . . . . . . . . . . . . 300

(SOIC - Lead Tips Only)

CAUTION: Stresses above those listed in "Absolute Maximum Ratings" may cause permanent damage to the device. This is a stress only rating and operation of the
device at these or any other conditions above those indicated in the operational sections of this specification is not implied.

NOTES:

1. Limiting input current to 100

A is recommended to avoid latchup problems. Typically 1mA is safe, however this is not guaranteed.

is measured with the component mounted on an evaluation PC board in free air.

Electrical Specifications

SUPPLY

5V. See Test Circuit, Unless Otherwise Specified

PARAMETER

SYMBOL

TEST CONDITIONS

TEMP.

(

MIN

TYP

MAX

UNITS

Input Offset Voltage (Note 3)

0.7

0 to 70

Average Temperature Coefficient of
Input Offset Voltage (Note 3)

0 to 70

0.02

Change in Input Offset with Time

100

nV/

month

Input Bias Current |I(+)|, |I(-)|

BIAS

0 to 70

Input Offset Current |I(-), |I(+)|

0 to 70

Input Resistance

Large Signal Voltage Gain (Note 3)

VOL

= 10k

, V

135

150

0 to 70

130

Output Voltage Swing (Note 4)

OUT

= 10k

4.7

4.85

= 100k

4.95

Common Mode Voltage Range (Note 3)

CMVR

-5

-5.2 to +4

3.5

0 to 70

-5

3.5

Common Mode Rejection Ratio
(Note 3)

CMRR

CMVR = -5V to +3.5V

120

140

0 to 70

120

Power Supply Rejection Ratio

PSRR

3V to

120

140

Input Noise Voltage

= 100

f = DC to 10Hz

P-P

Input Noise Current

f = 10Hz

0.01

pA/

Gain Bandwidth Product

GBWP

MHz

Slew Rate

= 50pF, R

= 10k

2.5

Rise Time

0.2

Overshoot

Operating Supply Range

V+ to V-

4.5

Supply Current

SUPP

No Load

0 to 70

3.2

Output Source Current

O SOURCE

2.9

4.5

0 to 70

2.3

ICL7650S

Test Circuit

Application Information

Detailed Description

AMPLIFIER

The functional diagram shows the major elements of the
ICL7650S. There are two amplifiers, the main amplifier, and the
nulling amplifier. Both have offset-null capability. The main
amplifier is connected continuously from the input to the output,
while the nulling amplifier, under the control of the chopping
oscillator and clock circuit, alternately nulls itself and the main
amplifier. The nulling connections, which are MOSFET gates,
are inherently high impedance, and two external capacitors
provide the required storage of the nulling potentials and the
necessary nulling-loop time constants. The nulling arrangement
operates over the full common-mode and power-supply ranges,
and is also independent of the output level, thus giving
exceptionally high CMRR, PSRR, and A

VOL

Careful balancing of the input switches, and the inherent
balance of the input circuit, minimizes chopper frequency
charge injection at the input terminals, and also the feed
forward-type injection into the compensation capacitor, which
is the main cause of output spikes in this type of circuit.

INTERMODULATION

Previous chopper-stabilized amplifiers have suffered from
intermodulation effects between the chopper frequency and
input signals. These arise because the finite AC gain of the

amplifier necessitates a small AC signal at the input. This is
seen by the zeroing circuit as an error signal, which is
chopped and fed back, thus injecting sum and difference
frequencies and causing disturbances to the gain and phase
vs frequency characteristics near the chopping frequency.
These effects are substantially reduced in the ICL7650S by
feeding the nulling circuit with a dynamic current,
corresponding to the compensation capacitor current, in such
a way as to cancel that portion of the input signal due to finite
AC gain. Since that is the major error contribution to the
ICL7650S, the intermodulation and gain/phase disturbances
are held to very low values, and can generally be ignored.

CAPACITOR CONNECTION

The null/storage capacitors should be connected to the
C

EXTA

and C

EXTB

pins, with a common connection to the

RETN

pin. This connection should be made directly by

either a separate wire or PC trace to avoid injecting load
current IR drops into the capacitive circuitry. The outside foil,
where available, should be connected to C

RETN

OUTPUT CLAMP

The OUTPUT CLAMP pin allows reduction of the overload
recovery time inherent with chopper-stabilized amplifiers.
When tied to the inverting input pin, or summing junction, a
current path between this point and the OUTPUT pin occurs
just before the device output saturates. Thus uncontrolled
input differentials are avoided, together with the consequent
charge buildup on the correction-storage capacitors. The
output swing is slightly reduced.

CLOCK

The ICL7650S has an internal oscillator, giving a chopping
frequency of 200Hz, available at the CLOCK OUT pin on the 14
pin devices. Provision has also been made for the use of an
external clock in these parts. The INT/EXT pin has an internal
pull-up and may be left open for normal operation, but to utilize
an external clock this pin must be tied to V- to disable the
internal clock. The external clock signal may then be applied to
the EXT CLOCK IN pin. An internal divide-by-two provides the

Output Sink Current

O SINK

0 to 70

Internal Chopping Frequency

Pins 13 and 14 Open

120

250

375

Clamp ON Current (Note 5)

= 100k

Clamp OFF Current (Note 5)

-4V

OUT

+4V

0.001

0 to 70

NOTES:

3. These parameters are guaranteed by design and characterization, but not tested at temperature extremes because thermocouple effects prevent

precise measurement of these voltages in automatic test equipment.

4. OUTPUT CLAMP not connected. See typical characteristic curves for output swing vs clamp current characteristics.
5. See OUTPUT CLAMP under detailed description.
6. All significant improvements over the industry-standard ICL7650 are highlighted in bold italics.

Electrical Specifications

SUPPLY

5V. See Test Circuit, Unless Otherwise Specified (Continued)

PARAMETER

SYMBOL

TEST CONDITIONS

TEMP.

(

MIN

TYP

MAX

UNITS

ICL7650S

OUTPUT

0.1

ICL7650S

desired 50% input switching duty cycle. Since the capacitors
are charged only when EXT CLOCK IN is high, a 50% - 80%
positive duty cycle is recommended, especially for higher
frequencies. The external clock can swing between V+ and V-.
The logic threshold will be at about 2.5V below V+. Note also
that a signal of about 400 Hz, with a 70% duty cycle, will be
present at the EXT CLOCK IN pin with INT/EXT high or open.
This is the internal clock signal before being fed to the divider.

In those applications where a strobe signal is available, an
alternate approach to avoid capacitor misbalancing during
overload can be used. If a strobe signal is connected to EXT
CLK IN so that it is low during the time that the overload
signal is applied to the amplifier, neither capacitor will be
charged. Since the leakage at the capacitor pins is quite low
at room temperature, the typical amplifier will drift less than
10

V/s, and relatively long measurements can be made with

little change in offset.

COMPONENT SELECTION

The two required capacitors, C

EXTA

and C

EXTB

, have

optimum values depending on the clock or chopping
frequency. For the preset internal clock, the correct value is
0.1

F, and to maintain the same relationship between the

chopping frequency and the nulling time constant this value
should be scaled approximately in proportion if an external
clock is used. A high quality film type capacitor such as
mylar is preferred, although a ceramic or other lower-grade
capacitor may prove suitable in many applications. For
quickest settling on initial turn-on, low dielectric absorption
capacitors (such as polypropylene) should be used. With
ceramic capacitors, several seconds may be required to
settle to 1

STATIC PROTECTION

All device pins are static-protected by the use of input diodes.
However, strong static fields and discharges should be avoided,
as they can cause degraded diode junction characteristics,
which may result in increased input-leakage currents.

LATCHUP AVOIDANCE

Junction-isolated CMOS circuits inherently include a parasitic
4-layer (PNPN) structure which has characteristics similar to
an SCR. Under certain circumstances this junction may be
triggered into a low-impedance state, resulting in excessive
supply current. To avoid this condition, no voltage greater than
0.3V beyond the supply rails should be applied to any pin. In
general, the amplifier supplies must be established either at
the same time or before any input signals are applied. If this is
not possible, the drive circuits must limit input current flow to
under 1mA to avoid latchup, even under fault conditions.

OUTPUT STAGE/LOAD DRIVING

The output circuit is a high-impedance type (approximately
18k

), and therefore with loads less than this value, the

chopper amplifier behaves in some ways like a
transconductance amplifier whose open-loop gain is

proportional to load resistance. For example, the open-loop
gain will be 17dB lower with a 1k

load than with a 10k

load. If the amplifier is used strictly for DC, this lower gain is
of little consequence, since the DC gain is typically greater
than 120dB even with a 1k

load. However, for wideband

applications, the best frequency response will be achieved
with a load resistor of 10k

or higher. This will result in a

smooth 6dB/octave response from 0.1Hz to 2MHz, with
phase shifts of less than 10 degrees in the transition region
where the main amplifier takes over from the null amplifier.

THERMO-ELECTRIC EFFECTS

The ultimate limitations to ultra-high precision DC amplifiers are
the thermo-electric or Peltier effects arising in thermocouple
junctions of dissimilar metals, alloys, silicon, etc. Unless all
junctions are at the same temperature, thermoelectric voltages
typically around 0.1

C, but up to tens of mV/

C for some

materials, will be generated. In order to realize the extremely
low offset voltages that the chopper amplifier can provide, it is
essential to take special precautions to avoid temperature
gradients. All components should be enclosed to eliminate air
movement, especially that caused by power-dissipating
elements in the system. Low thermoelectric-efficient
connections should be used where possible and power supply
voltages and power dissipation should be kept to a minimum.
High-impedance loads are preferable, and good separation
from surrounding heat-dissipating elements is advisable.

GUARDING

Extra care must be taken in the assembly of printed circuit
boards to take full advantage of the low input currents of the
ICL7650S. Boards must be thoroughly cleaned with TCE or
alcohol and blown dry with compressed air. After cleaning,
the boards should be coated with epoxy or silicone rubber to
prevent contamination.

Even with properly cleaned and coated boards, leakage
currents may cause trouble, particularly since the input pins
are adjacent to pins that are at supply potentials. This
leakage can be significantly reduced by using guarding to
lower the voltage difference between the inputs and adjacent
metal runs. Input guarding of the 8-pin TO-99 package is
accomplished by using 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. The guard, which
is a conductive ring surrounding the inputs, is connected to a
low impedance point that is at approximately the same
voltage as the inputs. Leakage currents from high-voltage
pins are then absorbed by the guard.

ICL7650S

Ð­Ð»ÐµÐºÑ‚Ñ€Ð¾Ð½Ð½Ñ‹Ð¹ ÐºÐ¾Ð¼Ð¿Ð¾Ð½ÐµÐ½Ñ‚: ICL7650SCBA-1

ÐÐ»ÐµÐºÑ‚Ñ€Ð¾Ð½Ð½Ñ‹Ð¹ ÐºÐ¾Ð¼Ð¿Ð¾Ð½ÐµÐ½Ñ‚: ICL7650SCBA-1