lf442-mwa National Semiconductor Corporation, lf442-mwa Datasheet - Page 11

• Manufacturer Part Number: lf442-mwa
• Description: Dual Low Power Jfet Input Operational Amplifier
• Manufacturer: National Semiconductor Corporation

Typical Applications
(Continued)
Conventional Log Amplifier
00915514
R
= Tel Labs type Q81
T
Trim 5k for 10 µA through the 5k–120k combination
*1% film resistor
Unconventional Log Amplifier
00915515
Q1, Q2, Q3 are included on LM389 amplifier chip which is temperature-stabilized by the LM389 and Q2-Q3, which act as a heater-sensor pair.
Q1, the logging transistor, is thus immune to ambient temperature variation and requires no temperature compensation at all.
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