CLASS AB CONTROL

OUT

InP

InM

Copyright © 2016, Texas Instruments Incorporated

16

LMV341-N, LMV342-N, LMV344-N

SNOS990H – APRIL 2002 – REVISED JUNE 2016

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Product Folder Links: LMV341-N LMV342-N LMV344-N

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Copyright © 2002–2016, Texas Instruments Incorporated

7 Detailed Description

7.1 Overview

TI’s LMV34x-N family of amplifiers have 1-MHz bandwidth, 1-V/µs slew rate, a rail-to-rail output stage, and

consume only 100 µA of current per amplifier while active. When in shutdown mode it only consumes 45-pA

supply consumption with only 20 fA of input bias current. Lastly, these operational amplifiers provide an input-

referred voltage noise 29 nV

√Hz (at 10 kHz).

7.2 Functional Block Diagram

7.3 Feature Description

7.3.1 Class AB Turnaround Stage Amplifier

This patented folded cascode stage has a combined class AB amplifier stage, which replaces the conventional

folded cascode stage. Therefore, the class AB folded cascode stage runs at a much lower quiescent current

compared to conventional-folded cascode stages. This results in significantly smaller offset and noise

contributions. The reduced offset and noise contributions in turn reduce the offset voltage level and the voltage

noise level at the input of LMV34x-N. Also the lower quiescent current results in a high open-loop gain for the

amplifier. The lower quiescent current does not affect the slew rate of the amplifier nor its ability to handle the

total current swing coming from the input stage.

The input voltage noise of the device at low frequencies, below 1 kHz, is slightly higher than devices with a BJT

input stage; however, the PMOS input stage results in a much lower input bias current and the input voltage

noise drops at frequencies above 1 kHz.

7.4 Device Functional Modes

7.4.1 Shutdown Feature

The LMV341-N is capable of being turned off to conserve power and increase battery life in portable devices.

Once in shutdown mode the supply current is drastically reduced, 1-µA maximum, and the output is tri-stated.

The device is disabled when the shutdown pin voltage is pulled low. The shutdown pin must never be left

unconnected. Leaving the pin floating results in an undefined operation mode and the device may oscillate

between shutdown and active modes.

The LMV341-N typically turns on 2.8 µs after the shutdown voltage is pulled high. The device turns off in less

than 400 ns after shutdown voltage is pulled low. Figure 41 and Figure 42 show the turnon and turnoff time of the

LMV341-N, respectively. To reduce the effect of the capacitance added to the circuit by the scope probe, in the

turnoff time circuit a resistive load of 600

Ω is added. Figure 43 and Figure 44 show the test circuits used to

obtain the two plots.