説明

The LT1413 is a low cost, upgraded version of Linear Technology’s industry standard LT1013 dual, single supply op amp. The LT1413 is optimized for single 5V applications, although ±15V specifications are also provided for completeness. In the design of the LT1413, particular emphasis has been placed on low cost plastic and SO-8 package performance: 60µV offset voltage, 0.1nA offset current, in excess of 10mA output current at 330µA supply current and 140dB channel separation are some of the specifications achieved. Other dual, single supply amplifiers are available to complement the LT1413 family: the micropower LT1078’s supply current is 10 times lower with a 4.5 fold speed performance degradation compared to the LT1413. Conversely, the LT1211, LT1213 and LT1215 duals have 4 to 14 times higher supply current, but also 13 to 50 times higher speed.

 

特徴

Single Supply Operation:

Input Goes Below Ground

Output Swings to Ground Sinking Current

No Pull-Down Resistors Needed

Phase Reversal Protection

At 5V, 0V Low Cost Grade Specifications:

280µV Max Offset Voltage

380µV Max in S8 Package

0.8nA Max Offset Current

480µA Max Supply Current per Amplifier

0.5µV/°C Drift

1.4 Million Voltage Gain

950kHz Gain-Bandwidth Product

0.55µVP-P, 0.1Hz to 10Hz Noise

 

アプリケーション

Single Supply Systems

Two and Three Op Amp Instrumentation Amplifiers

Active Filters

Battery-Powered Systems

Strain Gauge and Bridge Amplifiers

 

アプリケーション情報

Single Supply Operation

The LT1413 is fully specified for single supply operation, i.e., when the negative supply is 0V. Input common-mode range includes ground; the output swings within a few millivolts of ground. If the input is more than a few hundred millivolts below ground, two distinct problems can occur on previous single supply designs, such as the LM124, LM158, OP-21 and OP-221. a) When the input is more than a diode drop below ground, unlimited current will flow from the substrate (V– terminal) to the input. This can destroy the unit. On the LT1413, the 400Ω resistors, in series with the input (see Schematic Diagram), protect the devices even when the input is 5V below ground. b) When the input is more than 400mV below ground (at 25°C), the input stage saturates (transistors Q3 and Q4) and phase reversal occurs at the output. This can cause lock-up in servo systems. Due to a unique phase reversal protection circuitry (Q21, Q22, Q27, Q28), the LT1413 outputs do not reverse, as illustrated below, even when the inputs are at –1.5V. Keep the output of the  other amplifier out of negative saturation for the phase reversal protection to function properly. Since the output of the LT1413 cannot go exactly to ground, but can only approach ground to within a few millivolts, care should be exercised to ensure that the output is not saturated. For example, a 1mV input signal will cause the amplifier to set up in its linear region in the gain 100 configuration shown below, but is not enough to make the amplifier function properly in the voltage-follower mode.

Comparator Applications

The single supply operation of the LT1413 lends itself to its use as a precision comparator with TTL compatible output; the response time is shown below.