V

+

+

-

+

-

V

+

C = 200pF

SAMPLE

CLOCK

Copyright © 2016, Texas Instruments Incorporated

18

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

8 Application and Implementation

NOTE

Information in the following applications sections is not part of the TI component

specification, and TI does not warrant its accuracy or completeness. TI’s customers are

responsible for determining suitability of components for their purposes. Customers should

validate and test their design implementation to confirm system functionality.

8.1 Application Information

The LMV34x-N amplifier family features low voltage, low power, rail-to-rail output as well as a shutdown

capability, making it well suited for low voltage portable applications.

8.2 Typical Application

8.2.1 Sample and Hold Circuit

Figure 46. Sample and Hold Circuit

8.2.1.1 Design Requirements

The lower input bias current of the LMV341-N results in a very high input impedance. The output impedance

when the device is in shutdown mode is quite high. These high impedances, along with the ability of the

shutdown pin to be derived from a separate power source, make LMV341-N a good choice for sample and hold

circuits. The sample clock must be connected to the shutdown pin of the amplifier to rapidly turn the device on or

off.

8.2.1.2 Detailed Design Procedure

Figure 46 shows the schematic of a simple sample and hold circuit. When the sample clock is high the first

amplifier is in normal operation mode and the second amplifier acts as a buffer. The capacitor, which appears as

a load on the first amplifier, is charging at this time. The voltage across the capacitor is that of the noninverting

input of the first amplifier because it is connected as a voltage-follower. When the sample clock is low the first

amplifier is shut off, bringing the output impedance to a high value. The high impedance of this output, along with

the very high impedance on the input of the second amplifier, prevents the capacitor from discharging. There is

very little voltage droop while the first amplifier is in shutdown mode. The second amplifier, which is still in normal

operation mode and is connected as a voltage follower, also provides the voltage sampled on the capacitor at its

output.