LM194

Supermatch Pair

Other names for this product: LM394,

Courtesy/Thanks to: National Semiconductor

Description: The LM194 and LM394 are junction isolated ultra wellmatched monolithic NPN transistor pairs with an order of magnitude improvement in matching over conventional tran- sistor pairs. This was accomplished by advanced linear pro- cessing and a unique new device structure. Electrical characteristics of these devices such as drift ver- sus initial offset voltage, noise, and the exponential relation- ship of base-emitter voltage to collector current closely ap- proach those of a theoretical transistor. Extrinsic emitter and base resistances are much lower than presently avail- able pairs, either monolithic or discrete, giving extremely low noise and theoretical operation over a wide current range. Most parameters are guaranteed over a current range of 1 mA to 1 mA and 0V up to 40V collector-base voltage, ensuring superior performance in nearly all applications. To guarantee long term stability of matching parameters, internal clamp diodes have been added across the emitter- base junction of each transistor. These prevent degradation due to reverse biased emitter currentÐthe most common cause of field failures in matched devices. The parasitic iso- lation junction formed by the diodes also clamps the sub- strate region to the most negative emitter to ensure com- plete isolation between devices. The LM194 and LM394 will provide a considerable improve- ment in performance in most applications requiring a closely matched transistor pair. In many cases, trimming can be eliminated entirely, improving reliability and decreasing costs. Additionally, the low noise and high gain make this device attractive even where matching is not critical. The LM194 and LM394/LM394B/LM394C are available in an isolated header 6-lead TO-5 metal can package. The LM394/LM394B/LM394C are available in an 8-pin plastic dual-in-line package. The LM194 is identical to the LM394 except for tighter electrical specifications and wider temperature range.

Features
- Emitter-base voltage matched to 50 mV
- Offset voltage drift less than 0.1 mV/§C
- Current gain (hFE) matched to 2%
- Common-mode rejection ratio greater than 120 dB
- Parameters guaranteed over 1 mA to 1 mA collector current
- Extremely low noise
- Superior logging characteristics compared to conventional pairs
- Plug-in replacement for presently available devices