LMV324 datasheet(9/21 Pages) ONSEMI

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LMV321 / LMV358 / LMV324 Rev. 2.9

Application Information

General Description

The LMV3XX family are single supply, general-purpose,

voltage-feedback amplifiers that are pin-for-pin compati-

ble and drop in replacements with other industry standard

LMV321, LMV358, and LMV324 amplifiers. The LMV3XX

family is fabricated on a CMOS process, features a rail-

to-rail output, and is unity gain stable.

The typical non-inverting circuit schematic is shown in

Figure1.

Figure 1. Typical Non-inverting configuration

Power Dissipation

The maximum internal power dissipation allowed is di-

rectly related to the maximum junction temperature. If the

maximum junction temperature exceeds 150°C, some

performance degradation will occur. If the maximum junc-

tion temperature exceeds 175°C for an extended time,

device failure may occur.

Driving Capacitive Loads

The Frequency Response vs. CL plot on page 4, illus-

trates the response of the LMV3XX family. A small series

resistance (RS) at the output of the amplifier, illustrated in

Figure 2, will improve stability and settling performance.

Rs values in the Frequency Response vs. CL plot were

chosen to achieve maximum bandwidth with less than

1dB of peaking. For maximum flatness, use a larger RS.

As the plot indicates, the LMV3XX family can easily drive

a 200 pF capacitive load without a series resistance. For

comparison, the plot also shows the LMV321 driving a

200 pF load with a 225

Ω series resistance.

Driving a capacitive load introduces phase-lag into the

output signal, which reduces phase margin in the amplifi-

er. The unity gain follower is the most sensitive configura-

tion. In a unity gain follower configuration, the LMV3XX

family requires a 450

Ω series resistor to drive a 200 pF

load. The response is illustrated in Figure 3.

Figure 2. Typical Topology for driving a capacitive

load

Figure 3. Frequency Response vs. CL for unity gain

configuration

Layout Considerations

General layout and supply bypassing play major roles in

high frequency performance. Fairchild has evaluation

boards to use as a guide for high frequency layout and as

aid in device testing and characterization. Follow the

steps below as a basis for high frequency layout:

• Include 6.8

μF and 0.01 μF ceramic capacitors

• Place the 6.8

μF capacitor within 0.75 inches of the

power pin

• Place the 0.01

μF capacitor within 0.1 inches of the

power pin

• Remove the ground plane under and around the part,

especially near the input and output pins to reduce

parasitic capacitance

• Minimize all trace lengths to reduce series

inductances

Refer to the evaluation board layouts shown in Figure 5

on page 8 for more information.

LMV3XX

0.01

μF

6.8

μF

Out

+In

+Vs

10k

LMV3XX

Frequency (M H z )

0.01

0.1

-9

-8

-7

-6

-5

-4

-3

-2

-1

CL = 50pF

Rs = 0

CL = 100pF

Rs = 400

CL = 200pF

Rs = 450

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