Datasheet

LMV2011

SNOSA32C –AUGUST 2003–REVISED MARCH 2013

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In the case of the inverting configuration, it is also possible to increase the input impedance of the overall

amplifier, by raising the value of R1, without having to increase the feed-back resistor, R2, to impractical values,

by utilizing a "Tee" network as feedback. See the LMC6442 data sheet (Application Notes section) for more

details on this.

Figure 36. AC Coupled ADC Driver

LMV2011 AS ADC INPUT AMPLIFIER

The LMV2011 is a great choice for an amplifier stage immediately before the input of an ADC (Analog-to-Digital

Converter), whether AC or DC coupled. See Figure 36 and Figure 37. This is because of the following important

characteristics:

A) Very low offset voltage and offset voltage drift over time and temperature allow a high closed-loop gain

setting without introducing any short-term or long-term errors. For example, when set to a closed-loop gain

of 100 as the analog input amplifier for a 12-bit A/D converter, the overall conversion error over full

operation temperature and 30 years life of the part (operating at 50°C) would be less than 5 LSBs.

B) Fast large-signal settling time to 0.01% of final value (1.4μs) allows 12 bit accuracy at 100KH

or more

sampling rate.

C) No flicker (1/f) noise means unsurpassed data accuracy over any measurement period of time, no matter

how long. Consider the following opamp performance, based on a typical low-noise, high-performance

commercially-available device, for comparison:

Opamp flatband noise = 8nV/√Hz

1/f corner frequency = 100Hz

= 2000

Measurement time = 100 sec

Bandwidth = 2Hz

This example will result in about 2.2 mV

(1.9 LSB) of output noise contribution due to the opamp alone,

compared to about 594μV

(less than 0.5 LSB) when that opamp is replaced with the LMV2011 which

has no 1/f contribution. If the measurement time is increased from 100 seconds to 1 hour, the

improvement realized by using the LMV2011 would be a factor of about 4.8 times (2.86mV

compared to

596μV when LMV2011 is used) mainly because the LMV2011 accuracy is not compromised by increasing

the observation time.

D) Copper leadframe construction minimizes any thermocouple effects which would degrade low level/high

gain data conversion application accuracy (see THE BENEFITS OF LMV2011 NO 1/f NOISE).

E) Rail-to-Rail output swing maximizes the ADC dynamic range in 5-Volt single-supply converter applications.

Below are some typical block diagrams showing the LMV2011 used as an ADC amplifier (Figure 36 and

Figure 37).

Product Folder Links: LMV2011