Excellent Dynamic Range
Wide Bandwidth
Built-In Temperature Compensation
Log Linearity (30 dB Sections) . . . 1 dB Typ
Wide Input Voltage Range

description
This monolithic amplifier circuit contains four
30-dB logarithmic stages. Gain in each stage is
such that the output of each stage is proportional
to the logarithm of the input voltage over the 30-dB
input voltage range. Each half of the circuit
contains two of these 30-dB stages summed
together in one differential output that is
proportional to the sum of the logarithms of the
input voltages of the two stages. The four stages
may be interconnected to obtain a theoretical
input voltage range of 120-dB. In practice, this
permits the input voltage range to be typically
greater than 80-dB with log linearity of ± 0.5-dB
(see application data). Bandwidth is from dc to
40 MHz.
This circuit is useful in military weapons systems,
broadband radar, and infrared reconnaissance
systems. It serves for data compression and
analog compensation. This logarithmic amplifier
is used in log IF circuitry as well as video and log
amplifiers. The TL441AM is characterized for
operation over the full military temperature range
of – 55°C to 125°C.