Datasheet

0.1
100
100k
10
100
1000
10000
1k
10
1M
FREQUENCY (Hz)
10k
1
VOLTAGE NOISE (nV/
Hz)
V
S
= 5V
LMP2011, LMP2012
www.ti.com SNOSA71K –OCTOBER 2004–REVISED MARCH 2013
MORE BENEFITS
The LMP201X offers the benefits mentioned above and more. It has a rail-to-rail output and consumes only 950
µA of supply current while providing excellent DC and AC electrical performance. In DC performance, the
LMP201X achieves 130 dB of CMRR, 120 dB of PSRR and 130 dB of open loop gain. In AC performance, the
LMP201X provides 3 MHz of gain-bandwidth product and 4 V/µs of slew rate.
HOW THE LMP201X WORKS
The LMP201X uses new, patented techniques to achieve the high DC accuracy traditionally associated with
chopper-stabilized amplifiers without the major drawbacks produced by chopping. The LMP201X continuously
monitors the input offset and corrects this error. The conventional chopping process produces many mixing
products, both sums and differences, between the chopping frequency and the incoming signal frequency. This
mixing causes large amounts of distortion, particularly when the signal frequency approaches the chopping
frequency. Even without an incoming signal, the chopper harmonics mix with each other to produce even more
trash. If this sounds unlikely or difficult to understand, look at the plot (Figure 32), of the output of a typical
(MAX432) chopper-stabilized op amp. This is the output when there is no incoming signal, just the amplifier in a
gain of -10 with the input grounded. The chopper is operating at about 150 Hz; the rest is mixing products. Add
an input signal and the noise gets much worse. Compare this plot with Figure 33 of the LMP201X. This data was
taken under the exact same conditions. The auto-zero action is visible at about 30 kHz but note the absence of
mixing products at other frequencies. As a result, the LMP201X has very low distortion of 0.02% and very low
mixing products.
Figure 32. The Output of a Chopper Stabilized Op Amp (MAX432)
Figure 33. The Output of the LMP2011/LMP2012
Copyright © 2004–2013, Texas Instruments Incorporated Submit Documentation Feedback 11
Product Folder Links: LMP2011 LMP2012