High Speed, 200 dB Range,
Logarithmic Converter
ADL5304 Data Sheet
FEATURES A single positive supply of 5 V is all that is required for operation
over a specified 1 pA to 3 mA input range. Dual-supply operation
extends the specified input current range to 10 mA. Optimized for very fast response at all input currents
Overall bandwidth of >4 MHz for inputs >1 µA
Bandwidth: 25 kHz at input of 1 nA and 350 kHz at 10 nA
10 decades of input range: 1 pA to 10 mA
Law conformance: ±0.25 dB from 100 pA to 100 µA
Log ratio or fixed-intercept operation
Precision voltage references and reference current
Adaptive photodiode (PD) bias for low dark current
Programmable log slope and intercept
Default log slope of 10 mV/dB at VLOG pin
Single-or dual-supply operation The ADL5304 accepts two current inputs to the logarithmic
argument. The numerator input, INUM, flows in the collector of an
NPN transistor, connected in a feedback path around a low offset
JFET amplifier. The denominator current, IDEN, is treated in the
same way, which allows for log ratio operation. The input summing
nodes (INUM and IDEN) operate at a constant default voltage of
1.5 V. The VSM1 to VSM4 pins flank the INUM and IDEN inputs
to provide a guard voltage to minimize leakage currents. …