LMV321 / LMV358 / LMV324 — General-Purpose, Low Voltage, Rail-to-Rail Output Amplifiers
Application Information
General Descri ption
The LMV3XX family are single supply, general-purpose,
voltage-feedback amplifiers that are pin-for-pin compati-
ble and drop in re placements 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 po wer dissipat ion allowed is di-
rectly related to the maximum juncti on temperature. If the
maximum junction temperature exceeds 150°C, some
performance de gradation 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 resp onse of the LMV3XX family . A small series
resistance (RS) at the output of the amplifier, illustrate d in
Figure 2, will improve stability and settling performance.
Rs values in the Frequen cy Response vs. CL pl ot were
chosen to achieve maximum bandwidth with less than
1dB of peaking. For maximum flatness, use a larger RS.
As the plot indi cates, the LMV3XX famil y can easily drive
a 200 pF capac itive lo ad without a series res istance . 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 mo st sensitive config ura-
tion. In a unity gain follower configuration, the LMV3XX
family r equires 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 Res ponse vs. CL for unity gain
configuration
Layout Considerations
General layout and supply bypassing play major roles
in high frequency performance. ON Semiconductor 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.
Ω
Frequency (MHz)
0.01 0.1 1 10
-9
-8
-7
-6
-5
-4
-2
-1
0
1
2
3
C
L
= 50pF
R
s
= 0
C
L
= 100pF
s
= 400Ω
C
L
= 200pF
R
s
= 450Ω
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