Datasheet LT1112, LT1114 (Analog Devices) - 10

LT1112/LT1114
U U W U APPLICATIO S I FOR ATIO
The LT1112 dual and LT1114 quad in the plastic and output clips cleanly, without any glitches or phase rever- ceramic DIP packages are pin compatible to and directly sal. The OP-297 exhibits phase reversal. The photos also replace such precision op amps as the OP-200, OP-297, illustrate that both the input and output ranges of the AD706 duals and OP-400, OP-497, AD704 quads with LT1112 are within 800mV of the supplies. The effect of improved price/performance. input and output overdrive on the other amplifiers in the LT1112 or LT1114 packages is negligible, as each The LT1112 in the S8 surface mount package has the amplifier is biased independently. standard pin configuration, i.e., the same configuration as the plastic and ceramic DIP packages.
Advantages of Matched Dual and Quad Op Amps
The LT1114 quad is offered in the narrow 16-pin surface In many applications the performance of a system de- mount package. All competitors are in the wide 16-pin pends on the matching between two operational amplifiers package which occupies 1.8 times the area of the narrow rather than the individual characteristics of the two op package. The wide package is also 1.8 times thicker than amps. Two or three op amp instrumentation amplifiers, the narrow package. tracking voltage references and low drift active filters are The inputs of the LT1112/1114 are protected with back-to- some of the circuits requiring matching between two op back diodes. In the voltage follower configuration, when amps. the input is driven by a fast large-signal pulse (>1V), the The well-known triple op amp configuration illustrates input protection diodes effectively short the output to the these concepts. Output offset is a function of the difference input during slewing, and a current, limited only by the between the offsets of the two halves of the LT1112. This output short-circuit protection, will flow through the error cancellation principle holds for a considerable num- diodes. ber of input referred parameters in addition to offset The use of a feedback resistor is recommended because voltage and its drift with temperature. Input bias current this resistor keeps the current below the short-circuit will be the average of the two noninverting input currents limit, resulting in faster recovery and settling of the output. (I + + B ). The difference between these two currents (∆IB ) is the offset current of the instrumentation amplifier. Com- The input voltage of the LT1112/1114 should never ex- mon mode and power supply rejections will be dependent ceed the supply voltages by more than a diode drop. only on the match between the two amplifiers (assuming However, the example below shows that as the input perfect resistor matching). voltage exceeds the common mode range, the LT1112’s
Voltage Follower with Input Exceeding the Common Mode Range (VS =
±
5V)
INPUT: ±5.2V Sine Wave LT1112 Output OP-297 Output 111214fb 10