LM194/LM394 December 1994 LM194/LM394 Supermatch Pair General Description Supermatch The LM194 and LM394 are junction isolated ultra well- matched transistor pair. In many cases, trimming can be matched monolithic NPN transistor pairs with an order of eliminated entirely, improving reliability and decreasing magnitude improvement in matching over conventional tran- costs. Additionally, the low noise and high gain make this sistor pairs. This was accomplished by advanced linear pro- device attractive even where matching is not critical. cessing and a unique new device structure. The LM194 and LM394/LM394B/LM394C are available in Electrical characteristics of these devices such as drift ver- an isolated header 6-lead TO-5 metal can package. The sus initial offset voltage, noise, and the exponential relation- LM394/LM394B/LM394C are available in an 8-pin plastic ship of base-emitter voltage to collector current closely ap- dual-in-line package. The LM194 is identical to the LM394 proach those of a theoretical transistor. Extrinsic emitter except for tighter electrical specifications and wider temper- Pair and base resistances are much lower than presently avail- ature range. able pairs, either monolithic or discrete, giving extremely low noise and theoretical operation over a wide current range. Features Most parameters are guaranteed over a current range of Y Emitter-base voltage matched to 50 mV 1 mA to 1 mA and 0V up to 40V collector-base voltage, Y Offset voltage drift less than 0.1 mV/§C ensuring superior performance in nearly all applications. Y Current gain (hFE) matched to 2% To guarantee long term stability of matching parameters, Y Common-mode rejection ratio greater than 120 dB internal clamp diodes have been added across the emitter- Y Parameters guaranteed over 1 mA to 1 mA collector base junction of each transistor. These prevent degradation current due to reverse biased emitter currentÐthe most common Y cause of field failures in matched devices. The parasitic iso- Extremely low noise lation junction formed by the diodes also clamps the sub- Y Superior logging characteristics compared to strate region to the most negative emitter to ensure com- conventional pairs plete isolation between devices. Y Plug-in replacement for presently available devices The LM194 and LM394 will provide a considerable improve- ment in performance in most applications requiring a closely Typical Applications Low Cost Accurate Square Root Circuit Low Cost Accurate Squaring Circuit I I OUT e 10b5. 010 VIN OUT e 10b6 (VIN)2 TL/H/9241 – 2 TL/H/9241 – 1 *Trim for full scale accuracy C1995 National Semiconductor Corporation TL/H/9241 RRD-B30M115/Printed in U. S. A.
