(0.1Hz to 1Hz)............................................ 0.65µV
P-P
■Pin Compatible With ICL7650
■Lower System Parts Count
ORDERING INFORMATION
Maximum
TemperatureOffset
Part No.PackageRangeVoltage
TC911ACOA8-Pin SOIC0°C to +70°C15µV
TC911ACPA8-Pin0°C to +70°C15µV
Plastic DIP
TC911BCOA8-Pin SOIC0°C to +70°C30µV
TC911BCPA8-Pin0°C to +70°C30µV
Plastic DIP
GENERAL DESCRIPTION
The TC911 CMOS auto-zeroed operational amplifier
is the first complete monolithic chopper-stabilized amplifier. Chopper operational amplifiers like the ICL7650/7652
and LTC1052 require user-supplied, external offset compensation storage capacitors. External capacitors arenot required with the TC911. Just as easy to use as the
conventional OP07 type amplifier, the TC911 significantly
reduces offset voltage errors. Pinout matches the OP07/
741/7650 8-pin mini-DIP configuration.
Several system benefits arise by eliminating the external chopper capacitors: lower system parts count, reduced
assembly time and cost, greater system reliability, reduced
PC board layout effort and greater board area utilization.
Space savings can be significant in multiple-amplifier designs.
Electrical specifications include 15µV maximum offset
voltage, 0.15µV/°C maximum offset voltage temperature
coefficient. Offset voltage error is five times lower than the
premium OP07E bipolar device. The TC911 improves offset drift performance by eight times.
The TC911 operates from dual or single power supplies. Supply current is typically 350µA. Single 4.5V to 16V
supply operation is possible, making single 9V battery
operation possible. The TC911 is available in 2 package
types: 8-pin plastic DIP and SOIC.
*Static-sensitive device. Unused devices should be stored in conductive
material. Stresses above 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
above those indicated in the operational sections of the specifications is not
implied.
C Device ................................................ 0°C to +70°C
The CMOS TC911 is pin compatible with the industry
standard ICL7650 chopper-stabilized amplifier. The ICL7650
must use external 0.1µF capacitors connected at pins 1 and
8. With the TC911, external offset voltage error cancel-ing capacitors are not required. On the TC911 pins 1, 8
and 5 are not connected internally. The ICL7650 uses pin 5
as an optional output clamp connection. External chopper
capacitors and clamp connections are not necessary with
the TC911. External circuits connected to pins 1, 8 and 5 will
have no effect. The TC911 can be quickly evaluated in
existing ICL7650 designs. Since external capacitors are not
required, system part count, assembly time, and total system cost are reduced. Reliability is increased and PC board
layout eased by having the error storage capacitors integrated on the TC911 chip.
The TC911 pinout matches many existing op-amps:
741, LM101, LM108, OP05–OP08, OP-20, OP-21, ICL7650
and ICL7652. In many applications operating from +5V
supplies the TC911 offers superior electrical performance
and can be a functional pin-compatible replacement. Offset
voltage correction potentiometers, compensation capacitors, and chopper-stabilization capacitors can be removed
when retrofitting existing equipment designs.
Thermocouple Errors
Heating one joint of a loop made from two different
metallic wires causes current flow. This is known as the
Seebeck effect. By breaking the loop, an open circuit voltage
J = J
3
4
J = J
J = J
J
J
NO TEMPERATURE DIFFERENTIAL
2
5
AND SAME METALLIC CONNECTION
1
6
3
4
J
2
J
1
J
6
PACKAGE
PIN
(Seebeck voltage) can be measured. Junction temperature and metal type determine the magnitude. Typical
values are 0.1µV/°C to 10µV/°C. Thermal-induced voltages
can be many times larger than the TC911 offset voltage drift.
Unless unwanted thermocouple potentials can be controlled, system performance will be less than optimum.
Unwanted thermocouple junctions are created when
leads are soldered or sockets/connectors are used. Low
thermo-electric coefficient solder can reduce errors. A 60%
Sn/36% Pb solder has 1/10 the thermal voltage of common
64% Sn/36% Pb solder at a copper junction.
The number and type of dissimilar metallic junctions in
the input circuit loop should be balanced. If the junctions are
kept at the same temperature, their summation will add to
zero-canceling errors (Figure 1).
Shielding precision analog circuits from air currents —
especially those caused by power dissipating components
and fans — will minimize temperature gradients and thermocouple-induced errors.
Avoiding Latch-Up
Junction-isolated CMOS circuits inherently contain a
parasitic p-n-p-n transistor circuit. Voltages exceeding the
supplies by 0.3V should not be applied to the device pins.
Larger voltages can turn the p-n-p-n device on, causing
excessive device power supply current and excessive power
dissipation. TC911 power supplies should be established at
the same time or before input signals are applied. If this is not
possible input current should be limited to 0.1mA to avoid
triggering the p-n-p-n structure.
Overload Recovery
The TC911 recovers quickly from the output saturation. Typical recovery time from positive output saturation is
20msec. Negative output saturation recovery time is typically 5msec.
J
5
J
2
+–+–
–
V
J
3
3
+
V = V + V + V – V – V – V = 0
T123456
+
V
J
4
4
–
Figure 1. Unwanted Thermocouple Errors Eliminated by
Reducing Thermal Gradients and Balancing Junctions
Information contained in this publication regarding device applications and the like is intended through suggestion only and may be superseded by
updates. It is your re sponsib ility to en sure that your applicati on mee ts with your specifica tions. No repr esentation or warra nty is given and no liability is
assumed by Micro chip Technology Incorporated with respe ct to the a ccuracy or use of such infor mati on, or infrin gemen t of patents or o th er int ell ec tua l
property rights arising from such use or otherwise. Use of Microchipís products as critical components in life support systems is not authorized except with
express written approval by Microchip. No licenses are conveyed, implicitly or otherwise, except as maybe explicitly expressed herein, under any intellectual property rights. The Mi crochip logo and name are registered trad emarks of Microchip Technology Inc. in the U.S.A. and other countries. All rights
reserved. All other trademarks mentioned herein are the property of their respective companies.
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