LMC6001_16 Datasheet, PDF (14/25 Pages) Texas Instruments – Ultra, Ultra-Low Input Current Amplifier

LMC6001
SNOS694I – MARCH 1995 – REVISED SEPTEMBER 2015
7 Detailed Description
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7.1 Overview
LMC6001 has an extremely low input current of 25 fA. In addition, its ultra-low input current noise of 0.13 fA/√Hz
allows almost noiseless amplification of high-resistance signal sources. LMC6001 is ideally suited for
electrometer applications requiring ultra-low input leakage current such as sensitive photodetection
transimpedance amplifiers and sensor amplifiers.
7.2 Functional Block Diagram
7.3 Feature Description
7.3.1 Amplifier Topology
The LMC6001 incorporates a novel op amp design topology that enables it to maintain rail-to-rail output swing
even when driving a large load. Instead of relying on a push-pull unity gain output buffer stage, the output stage
is taken directly from the internal integrator, which provides both low output impedance and large gain. Special
feed-forward compensation design techniques are incorporated to maintain stability over a wider range of
operating conditions than traditional op amps. These features make the LMC6001 both easier to design with, and
provide higher speed than products typically found in this low-power class.
7.3.2 Latch-Up Prevention
CMOS devices tend to be susceptible to latch-up due to their internal parasitic SCR effects. The (I/O) input and
output pins look similar to the gate of the SCR. There is a minimum current required to trigger the SCR gate
lead. The LMC6001 is designed to withstand 100-mA surge current on the I/O pins. Some resistive method
should be used to isolate any capacitance from supplying excess current to the I/O pins. In addition, like an SCR,
there is a minimum holding current for any latch-up mode. Limiting current to the supply pins will also inhibit
latch-up susceptibility.
7.4 Device Functional Modes
The LMC6001 has a single functional mode and operates according to the conditions listed in Recommended
Operating Conditions.
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