TC913B データシートの表示（PDF） - TelCom Semiconductor Inc => Microchip
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TC913B Datasheet PDF : 4 Pages
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DUAL AUTO-ZEROED
OPERATIONAL AMPLIFIERS
1
TC913A
TC913B
Theory of Operation
Each of the TC913's two op-amps actually consists of
two amplifiers. A main amplifier is always connected from
the input to the output. A separate nulling amplifier alter-
nately nulls its own offset and then the offset of the amplifier.
Since each amplifier is continuously being nulled, offset
voltage drift with time, temperature, and power supply
variations is greatly reduced.
All nulling circuitry is internal and the nulling operation is
transparent to the user. Offset nulling voltages are stored on
two internal capacitors. An internal oscillator and control
logic, shared by the TC913's two amplifiers, control the
nulling process.
Pin Compatibility
The TC913 pinout is compatible with OP-14, LM358,
MC1458, LT1013, TLC322, and similar dual op amps. In
many circuits operating from single or ±5V supplies, the
TC913 is a drop-in replacement offering DC performance
rivaling that of the best single op amps.
The TC913's amplifiers include a low-impedance class
AB output buffer. Some previous CMOS chopper amplifiers
used a high-impedance output stage which made open-loop
gain dependent on load resistance. The TC913's open-loop
gain is not dependent on load resistance.
Overload Recovery
The TC913 recovers quickly from output saturation.
Typical recovery time from positive output saturation is
20msec. Negative output saturation recovery time is typi-
cally 5msec.
Avoiding Latch-Up
2 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 power dissipa-
tion. The TC913's 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.
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TELCOM SEMICONDUCTOR, INC.
8
3-271
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