LMV821 Single/ LMV822 Dual/ LMV824 Quad
Low Voltage, Low Power, R-to-R Output, 5 MHz Op Amps
General Description
The LMV821/LMV822/LMV824 bring performance and
economy to low voltage / low power systems. Witha5MHz
unity-gain frequency and a guaranteed 1.4 V/µs slew rate,
the quiescent current is only 220 µA/amplifier (2.7 V). They
provide rail-to-rail (R-to-R) output swing into heavy loads
(600 ΩGuarantees). The input common-mode voltage range
includes ground, and the maximum input offset voltage is
3.5mV (Guaranteed). They are also capable of comfortably
driving large capacitive loads (refer to the application notes
section).
The LMV821 (single) is available in the ultra tiny SC70-5
package, which is about half the size of the previous title
holder, the SOT23-5.
Overall, the LMV821/LMV822/LMV824 (Single/Dual/Quad)
are low voltage, low power, performance op amps, that can
be designed into a wide range of applications, at an eco-
nomical price.
Features
(For Typical, 5 V Supply Values; Unless Otherwise Noted)
nUltra Tiny, SC70-5 Package 2.0 x 2.0 x 1.0 mm
nGuaranteed 2.5 V, 2.7 V and 5 V Performance
nMaximum VOS 3.5 mV (Guaranteed)
nVOS Temp. Drift 1 uV/˚ C
nGBW product @2.7 V 5 MHz
nI
Supply
@2.7 V 220 µA/Amplifier
nMinimum SR 1.4 V/us (Guaranteed)
nCMRR 90 dB
nPSRR 85 dB
nRail-to-Rail (R-to-R) Output Swing
—@600 ΩLoad 160 mV from rail
—@10 kΩLoad 55 mV from rail
nV
CM
@5 V -0.3 V to 4.3 V
nStable with High Capacitive Loads (Refer to Application
Section)
Applications
nCordless Phones
nCellular Phones
nLaptops
nPDAs
nPCMCIA
Telephone-line Transceiver for a PCMCIA Modem Card
DS100128-33
December 2000
LMV821 / LMV822 / LMV824 Single/Dual Quad Low Voltage, Low Power, RRO, 5 MHz Op Amps
© 2001 National Semiconductor Corporation DS100128 www.national.com
Absolute Maximum Ratings (Note 1)
If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales Office/
Distributors for availability and specifications.
ESD Tolerance (Note 2)
Machine Model 100V
Human Body Model
LMV822/824 2000V
LMV821 1500V
Differential Input Voltage ±Supply Voltage
Supply Voltage (V
+
–V
−
) 5.5V
Output Short Circuit to V
+
(Note 3)
Output Short Circuit to V
−
(Note 3)
Soldering Information
Infrared or Convection (20 sec) 235˚C
Storage Temperature Range −65˚C to 150˚C
Junction Temperature (Note 4) 150˚C
Operating Ratings (Note 1)
Supply Voltage 2.5V to 5.5V
Temperature Range
LMV821, LMV822, LMV824 −40˚C ≤T
J
≤85˚C
Thermal Resistance (θ
JA
)
Ultra Tiny SC70-5 Package
5-Pin Surface Mount 440 ˚C/W
Tiny SOT23-5 Package 5-Pin
Surface Mount 265 ˚C/W
SO Package, 8-Pin Surface
Mount 190 ˚C/W
MSOP Package, 8-Pin Mini
Surface Mount 235 ˚C/W
SO Package, 14-Pin Surface
Mount 145 ˚C/W
TSSOP Package, 14-Pin 155 ˚C/W
2.7V DC Electrical Characteristics
Unless otherwise specified, all limits guaranteed for T
J
= 25˚C. V
+
= 2.7V, V
−
= 0V, V
CM
= 1.0V, V
O
= 1.35V and R
L
>1MΩ.
Boldface limits apply at the temperature extremes.
Symbol Parameter Condition Typ
(Note 5) LMV821/822/824
Limit (Note 6) Units
V
OS
Input Offset Voltage 1 3.5 mV
4max
TCV
OS
Input Offset Voltage Average
Drift 1 µV/˚C
I
B
Input Bias Current 30 90 nA
140 max
I
OS
Input Offset Current 0.5 30 nA
50 max
CMRR Common Mode Rejection Ratio 0V ≤V
CM
≤1.7V 85 70 dB
68 min
+PSRR Positive Power Supply
Rejection Ratio 1.7V ≤V
+
≤4V, V
-
= 1V, V
O
=
0V, V
CM
=0V 85 75 dB
70 min
−PSRR Negative Power Supply
Rejection Ratio -1.0V ≤V
-
≤-3.3V, V
+
= 1.7V,
V
O
= 0V, V
CM
=0V 85 73 dB
70 min
V
CM
Input Common-Mode Voltage
Range For CMRR ≥50dB -0.3 -0.2 V
max
2.0 1.9 V
min
A
V
Large Signal Voltage Gain Sourcing, R
L
= 600Ωto 1.35V,
V
O
= 1.35V to 2.2V 100 90 dB
85 min
Sinking, R
L
= 600Ωto 1.35V,
V
O
= 1.35V to 0.5V 90 85 dB
80 min
Sourcing, R
L
=2kΩto 1.35V,
V
O
= 1.35V to 2.2V 100 95 dB
90 min
Sinking, R
L
=2kΩto 1.35, V
O
= 1.35 to 0.5V 95 90 dB
85 min
LMV821 Single/ LMV822 Dual/ LMV824 Quad
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2.7V DC Electrical Characteristics (Continued)
Unless otherwise specified, all limits guaranteed for T
J
= 25˚C. V
+
= 2.7V, V
−
= 0V, V
CM
= 1.0V, V
O
= 1.35V and R
L
>1MΩ.
Boldface limits apply at the temperature extremes.
Symbol Parameter Condition Typ
(Note 5) LMV821/822/824
Limit (Note 6) Units
V
O
Output Swing V
+
= 2.7V, R
L
= 600Ωto 1.35V 2.58 2.50 V
2.40 min
0.13 0.20 V
0.30 max
V
+
= 2.7V, R
L
=2kΩto 1.35V 2.66 2.60 V
2.50 min
0.08 0.120 V
0.200 max
I
O
Output Current Sourcing, V
O
=0V 16 12 mA
min
Sinking, V
O
= 2.7V 26 12 mA
min
I
S
Supply Current LMV821 (Single) 0.22 0.3 mA
0.5 max
LMV822 (Dual) 0.45 0.6 mA
0.8 max
LMV824 (Quad) 0.72 1.0 mA
1.2 max
2.5V DC Electrical Characteristics
Unless otherwise specified, all limits guaranteed for T
J
= 25˚C. V
+
= 2.5V, V
−
= 0V, V
CM
= 1.0V, V
O
= 1.25V and R
L
>1MΩ.
Boldface limits apply at the temperature extremes.
Symbol Parameter Condition Typ
(Note 5) LMV821/822/824
Limit (Note 6) Units
V
OS
Input Offset Voltage 1 3.5 mV
4max
V
O
Output Swing V
+
= 2.5V, R
L
= 600Ωto
1.25V 2.37 2.30 V
2.20 min
0.13 0.20 V
0.30 max
V
+
= 2.5V, R
L
=2kΩto 1.25V 2.46 2.40 V
2.30 min
0.08 0.12 V
0.20 max
2.7V AC Electrical Characteristics
Unless otherwise specified, all limits guaranteed for T
J
= 25˚C. V
+
= 2.7V, V
−
= 0V, V
CM
= 1.0V, V
O
= 1.35V and R
L
>1MΩ.
Boldface limits apply at the temperature extremes.
Symbol Parameter Conditions Typ
(Note 5) LMV821/822/824 Limit
(Note 6) Units
SR Slew Rate (Note 7) 1.5 V/µs
GBW Gain-Bandwdth Product 5 MHz
Φ
m
Phase Margin 61 Deg.
G
m
Gain Margin 10 dB
Amp-to-Amp Isolation (Note 8) 135 dB
e
n
Input-Related Voltage Noise f = 1 kHz, V
CM
=1V 28
LMV821 Single/ LMV822 Dual/ LMV824 Quad
www.national.com3
2.7V AC Electrical Characteristics (Continued)
Unless otherwise specified, all limits guaranteed for T
J
= 25˚C. V
+
= 2.7V, V
−
= 0V, V
CM
= 1.0V, V
O
= 1.35V and R
L
>1MΩ.
Boldface limits apply at the temperature extremes.
Symbol Parameter Conditions Typ
(Note 5) LMV821/822/824 Limit
(Note 6) Units
i
n
Input-Referred Current Noise f = 1 kHz 0.1
THD Total Harmonic Distortion f = 1 kHz, A
V
= −2,
R
L
=10kΩ,V
O
= 4.1 V
PP
0.01 %
5V DC Electrical Characteristics
Unless otherwise specified, all limits guaranteed for T
J
= 25˚C. V
+
= 5V, V
−
= 0V, V
CM
= 2.0V, V
O
= 2.5V and R
L
>1MΩ.
Boldface limits apply at the temperature extremes.
Symbol Parameter Condition Typ
(Note 5) LMV821/822/824
Limit (Note 6) Units
V
OS
Input Offset Voltage 1 3.5 mV
4.0 max
TCV
OS
Input Offset Voltage Average
Drift 1 µV/˚C
I
B
Input Bias Current 40 100 nA
150 max
I
OS
Input Offset Current 0.5 30 nA
50 max
CMRR Common Mode Rejection Ratio 0V ≤V
CM
≤4.0V 90 72 dB
70 min
+PSRR Positive Power Supply
Rejection Ratio 1.7V ≤V
+
≤4V, V
-
= 1V, V
O
=
0V, V
CM
=0V 85 75 dB
70 min
−PSRR Negative Power Supply
Rejection Ratio -1.0V ≤V
-
≤-3.3V, V
+
= 1.7V,
V
O
= 0V, V
CM
=0V 85 73 dB
70 min
V
CM
Input Common-Mode Voltage
Range For CMRR ≥50dB -0.3 -0.2 V
max
4.3 4.2 V
min
A
V
Large Signal Voltage Gain Sourcing, R
L
= 600Ωto 2.5V,
V
O
= 2.5 to 4.5V 105 95 dB
90 min
Sinking, R
L
= 600Ωto 2.5V,
V
O
= 2.5 to 0.5V 105 95 dB
90 min
Sourcing, R
L
=2kΩto 2.5V,
V
O
= 2.5 to 4.5V 105 95 dB
90 min
Sinking, R
L
=2kΩto 2.5, V
O
=
2.5 to 0.5V 105 95 dB
90 min
V
O
Output Swing V
+
= 5V,R
L
= 600Ωto 2.5V 4.84 4.75 V
4.70 min
0.17 0.250 V
.30 max
V
+
= 5V, R
L
=2kΩto 2.5V 4.90 4.85 V
4.80 min
0.10 0.15 V
0.20 max
LMV821 Single/ LMV822 Dual/ LMV824 Quad
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5V DC Electrical Characteristics (Continued)
Unless otherwise specified, all limits guaranteed for T
J
= 25˚C. V
+
= 5V, V
−
= 0V, V
CM
= 2.0V, V
O
= 2.5V and R
L
>1MΩ.
Boldface limits apply at the temperature extremes.
Symbol Parameter Condition Typ
(Note 5) LMV821/822/824
Limit (Note 6) Units
I
O
Output Current Sourcing, V
O
=0V 45 20 mA
15 min
Sinking, V
O
=5V 40 20 mA
15 min
I
S
Supply Current LMV821 (Single) 0.30 0.4 mA
0.6 max
LMV822 (Dual) 0.5 0.7 mA
0.9 max
LMV824 (Quad) 1.0 1.3 mA
1.5 max
5V AC Electrical Characteristics
Unless otherwise specified, all limits guaranteed for T
J
= 25˚C. V
+
= 5V, V
−
= 0V, V
CM
= 2V, V
O
= 2.5V and R
L
>1MΩ.
Boldface limits apply at the temperature extremes.
Symbol Parameter Conditions Typ
(Note 5) LMV821/822/824 Limit
(Note 6) Units
SR Slew Rate (Note 7) 2.0 1.4 V/µs
min
GBW Gain-Bandwdth Product 5.6 MHz
Φ
m
Phase Margin 67 Deg.
G
m
Gain Margin 15 dB
Amp-to-Amp Isolation (Note 8) 135 dB
e
n
Input-Related Voltage Noise f = 1 kHz, V
CM
=1V 24
i
n
Input-Referred Current Noise f = 1 kHz 0.25
THD Total Harmonic Distortion f = 1 kHz, A
V
= −2,
R
L
=10kΩ,V
O
= 4.1 V
PP
0.01 %
Note 1: Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Operating Ratings indicate conditions for which the device is
intended to be functional, but specific performance is not guaranteed. For guaranteed specifications and the test conditions, see the Electrical Characteristics.
Note 2: Human body model, 1.5 kΩin series wth 100 pF. Machine model, 200Ωin series with 100 pF.
Note 3: Applies to both single-supply and split-supply operation. Continuous short circuit operation at elevated ambient temperature can result in exceeding the
maximum allowed junction temperature of 150˚C. Output currents in excess of 45 mA over long term may adversely affect reliability.
Note 4: The maximum power dissipation is a function of TJ(max) ,θJA, and TA. The maximum allowable power dissipation at any ambient temperature is PD=
(TJ(max)–T A)/θJA. All numbers apply for packages soldered directly into a PC board.
Note 5: Typical Values represent the most likely parametric norm.
Note 6: All limits are guaranteed by testing or statistical analysis.
Note 7: V+= 5V. Connected as voltage follower with 3V step input. Number specified is the slower of the positive and negative slew rates.
Note 8: Input referred, V+= 5V and RL= 100kΩconnected to 2.5V. Each amp excited in turn with 1 kHz to produce V O=3V
PP.
LMV821 Single/ LMV822 Dual/ LMV824 Quad
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Typical Performance Characteristics Unless otherwise specified, V
S
= +5V, single supply, T
A
= 25˚C.
Supply Current vs. Supply Voltage (LMV821)
DS100128-1
Input Current vs. Temperature
DS100128-2
Sourcing Current vs. Output Voltage (V
S
= 2.7V)
DS100128-3
Sourcing Current vs Output Voltage (V
S
= 5V)
DS100128-4
Sinking Current vs. Output Voltage (V
S
= 2.7V)
DS100128-5
Sinking Current vs. Output Voltage (V
S
= 5V)
DS100128-6
LMV821 Single/ LMV822 Dual/ LMV824 Quad
www.national.com 6
Typical Performance Characteristics Unless otherwise specified, V
S
= +5V, single supply,
TA= 25˚C. (Continued)
Output Voltage Swing vs. Supply Voltage (R
L
=10kΩ)
DS100128-7
Output Voltage Swing vs. Supply Voltage (R
L
=2kΩ)
DS100128-86
Output Voltage Swing vs. Supply Voltage (R
L
= 600Ω)
DS100128-8
Output Voltage Swing vs. Load Resistance
DS100128-87
Input Voltage Noise vs. Frequency
DS100128-18
Input Current Noise vs. Frequency
DS100128-17
LMV821 Single/ LMV822 Dual/ LMV824 Quad
www.national.com7
Typical Performance Characteristics Unless otherwise specified, V
S
= +5V, single supply,
TA= 25˚C. (Continued)
Crosstalk Rejection vs. Frequency
DS100128-93
+PSRR vs. Frequency
DS100128-9
-PSRR vs. Frequency
DS100128-10
CMRR vs. Frequency
DS100128-47
Input Voltage vs. Output Voltage
DS100128-88
Gain and Phase Margin vs. Frequency
(R
L
= 100kΩ,2kΩ, 600Ω) 2.7V
DS100128-11
LMV821 Single/ LMV822 Dual/ LMV824 Quad
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Typical Performance Characteristics Unless otherwise specified, V
S
= +5V, single supply,
TA= 25˚C. (Continued)
Gain and Phase Margin vs. Frequency
(R
L
= 100kΩ,2kΩ, 600Ω)5V
DS100128-12
Gain and Phase Margin vs. Frequency
(Temp.= 25, -40, 85˚C, R
L
= 10kΩ) 2.7V
DS100128-13
Gain and Phase Margin vs. Frequency
(Temp.= 25, -40, 85 ˚C, R
L
= 10kΩ)5V
DS100128-14
Gain and Phase Margin vs. Frequency
(C
L
= 100pF, 200pF, 0pF, R
L
= 10kΩ)2.7V
DS100128-15
Gain and Phase Margin vs. Frequency
(C
L
= 100pF, 200pF, 0pF R
L
= 10kΩ)5V
DS100128-16
Gain and Phase Margin vs. Frequency (C
L
= 100pF,
200pF, 0pF R
L
= 600Ω) 2.7V
DS100128-19
LMV821 Single/ LMV822 Dual/ LMV824 Quad
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Typical Performance Characteristics Unless otherwise specified, V
S
= +5V, single supply,
TA= 25˚C. (Continued)
Gain and Phase Margin vs. Frequency
(C
L
= 100pF, 200pF, 0pF R
L
= 600Ω)5V
DS100128-20
Slew Rate vs. Supply Voltage
DS100128-62
Non-Inverting Large Signal Pulse Response
DS100128-21
Non-Inverting Small Signal Pulse Response
DS100128-24
Inverting Large Signal Pulse Response
DS100128-27
Inverting Small Signal Pulse Response
DS100128-30
LMV821 Single/ LMV822 Dual/ LMV824 Quad
www.national.com 10
Typical Performance Characteristics Unless otherwise specified, V
S
= +5V, single supply,
TA= 25˚C. (Continued)
APPLICATION NOTE
This application note is divided into two sections: design
considerations and Application Circuits.
1.0 Design Considerations
This section covers the following design considerations:
1. Frequency and Phase Response Considerations
2. Unity-Gain Pulse Response Considerations
3. Input Bias Current Considerations
1.1 Frequency and Phase Response Considerations
The relationship between open-loop frequency response
and open-loop phase response determines the closed-loop
stability performance (negative feedback). The open-loop
phase response causes the feedback signal to shift towards
becoming positive feedback, thus becoming unstable. The
further the output phase angle is from the input phase angle,
the more stable the negative feedback will operate. Phase
Margin (φ
m
) specifies this output-to-input phase relationship
at the unity-gain crossover point. Zero degrees of phase-
margin means that the input and output are completely in
phase with each other and will sustain oscillation at the
unity-gain frequency.
The AC tables show φ
m
for a no load condition. But φ
m
changes with load. The Gain and Phase margin vs Fre-
quency plots in the curve section can be used to graphically
determine the φ
m
for various loaded conditions. To do this,
examine the phase angle portion of the plot, find the phase
margin point at the unity-gain frequency, and determine how
far this point is from zero degree of phase-margin. The larger
the phase-margin, the more stable the circuit operation.
The bandwidth is also affected by load. The graphs of
Figure
1
and
Figure 2
provide a quick look at how various loads
affect the φ
m
and the bandwidth of the LMV821/822/824
family. These graphs show capacitive loads reducing both
φ
m
and bandwidth, while resistive loads reduce the band-
width but increase the φ
m
. Notice how a 600Ωresistor can be
added in parallel with 220 picofarads capacitance, to in-
crease the φ
m
20˚(approx.), but at the price of about a 100
kHz of bandwidth.
Overall, the LMV821/822/824 family provides good stability
for loaded condition.
THD vs. Frequency
DS100128-82
DS100128-60
FIGURE 1. Phase Margin vs Common Mode Voltage for
Various Loads
DS100128-61
FIGURE 2. Unity-Gain Frequency vs Common Mode
Voltage for Various Loads
LMV821 Single/ LMV822 Dual/ LMV824 Quad
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1.2 Unity Gain Pulse Response Considerations
A pull-up resistor is well suited for increasing unity-gain,
pulse response stability. For example, a 600 Ωpull-up resis-
tor reduces the overshoot voltage by about 50%, when
driving a 220 pF load.
Figure 3
shows how to implement the
pull-up resistor for more pulse response stability.
Higher capacitances can be driven by decreasing the value
of the pull-up resistor, but its value shouldn’t be reduced
beyond the sinking capability of the part. An alternate ap-
proach is to use an isolation resistor as illustrated in
Figure 4
.
Figure 5
shows the resulting pulse response from a LMV824,
while driving a 10,000pF load through a 20 Ωisolation
resistor.
1.3 Input Bias Current Consideration
Input bias current (I
B
) can develop a somewhat significant
offset voltage. This offset is primarily due to I
B
flowing
through the negative feedback resistor, R
F
. For example, if I
B
is 90nA(max room) and R
F
is 100 kΩ, then an offset of 9 mV
will be developed (V
OS
=I
B
xR
F
).Using a compensation resis-
tor (R
C
), as shown in
Figure 6
, cancels out this affect. But the
input offset current (I
OS
) will still contribute to an offset
voltage in the same manner - typically 0.05 mV at room
temp.
2.0 APPLICATION CIRCUITS
This section covers the following application circuits:
1. Telephone-Line Transceiver
2. “Simple” Mixer (Amplitude Modulator)
3. Dual Amplifier Active Filters (DAAFs)
•a. Low-Pass Filter (LPF)
•b. High-Pass Filter (HPF)
5. Tri-level Voltage Detector
2.1 Telephone-Line Transceiver
The telephone-line transceiver of
Figure 7
provides a full-
duplexed connection through a PCMCIA, miniature trans-
former. The differential configuration of receiver portion
(UR), cancels reception from the transmitter portion (UT).
Note that the input signals for the differential configuration of
UR, are the transmit voltage (Vt) and Vt/2. This is because
R
match
is chosen to match the coupled telephone-line imped-
ance; therefore dividing Vt by two (assuming R1 >>R
match
).
The differential configuration of UR has its resistors chosen
to cancel the Vt and Vt/2 inputs according to the following
equation:
DS100128-41
FIGURE 3. Using a Pull-up Resistor at the Output for
Stabilizing Capacitive Loads
DS100128-43
FIGURE 4. Using an Isolation Resistor to Drive Heavy
Capacitive Loads
DS100128-54
FIGURE 5. Pulse Response per
Figure 4
DS100128-59
FIGURE 6. Canceling the Voltage Offset Effect of Input
Bias Current
LMV821 Single/ LMV822 Dual/ LMV824 Quad
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Note that Cr is included for canceling out the inadequacies of
the lossy, miniature transformer. Refer to application note
AN-397 for detailed explanation.
2.2“Simple” Mixer (Amplitude Modulator)
The mixer of
Figure 8
is simple and provides a unique form
of amplitude modulation. Vi is the modulation frequency
(F
M
), while a +3V square-wave at the gate of Q1, induces a
carrier frequency (F
C
). Q1 switches (toggles) U1 between
inverting and non-inverting unity gain configurations. Offset-
ting a sine wave above ground at Vi results in the oscillo-
scope photo of
Figure 9
.
The simple mixer can be applied to applications that utilize
the Doppler Effect to measure the velocity of an object. The
difference frequency is one of its output frequency compo-
nents. This difference frequency magnitude (/F
M
-F
C
/) is the
key factor for determining an object’s velocity per the Dop-
pler Effect. If a signal is transmitted to a moving object, the
reflected frequency will be a different frequency. This differ-
ence in transmit and receive frequency is directly propor-
tional to an object’s velocity.
2.4 Dual Amplifier Active Filters (DAAFs)
The LMV822/24 bring economy and performance to DAAFs.
The low-pass and the high-pass filters of
Figure 10
and
Figure 11
(respectively), offer one key feature: excellent
sensitivity performance. Good sensitivity is when deviations
in component values cause relatively small deviations in a
filter’s parameter such as cutoff frequency (Fc). Single am-
plifier active filters like the Sallen-Key provide relatively poor
sensitivity performance that sometimes cause problems for
high production runs; their parameters are much more likely
to deviate out of specification than a DAAF would. The
DAAFs of
Figure 10
and
Figure 11
are well suited for high
volume production.
DS100128-33
FIGURE 7. Telephone-line Transceiver for a PCMCIA
Modem Card
DS100128-39
FIGURE 8. Amplitude Modulator Circuit
f
f
mod
carrier
DS100128-40
FIGURE 9. Output signal per the Circuit of
Figure 8
DS100128-36
FIGURE 10. Dual Amplifier, 3 kHz Low-Pass Active
Filter with a Butterworth Response and a Pass Band
Gain of Times Two
LMV821 Single/ LMV822 Dual/ LMV824 Quad
www.national.com13
Table 1 provides sensitivity measurements for a 10 MΩload
condition. The left column shows the passive components
for the 3 kHz low-pass DAAF. The third column shows the
components for the 300 Hz high-pass DAAF. Their respec-
tive sensitivity measurements are shown to the right of each
component column. Their values consists of the percent
change in cutoff frequency (Fc) divided by the percent
change in component value. The lower the sensitivity value,
the better the performance.
Each resistor value was changed by about 10 percent, and
this measured change was divided into the measured
change in Fc. A positive or negative sign in front of the
measured value, represents the direction Fc changes rela-
tive to components’ direction of change. For example, a
sensitivity value of negative 1.2, means that for a 1 percent
increase in component value, Fc decreases by 1.2 percent.
Note that this information provides insight on how to fine
tune the cutoff frequency, if necessary. It should be also
noted that R
4
and R
5
of each circuit also caused variations in
the pass band gain. Increasing R
4
by ten percent, increased
the gain by 0.4 dB, while increasing R
5
by ten percent,
decreased the gain by 0.4 dB.
TABLE 1.
Component
(LPF) Sensitivity
(LPF) Component
(HPF) Sensitivity
(HPF)
R
a
-1.2 C
a
-0.7
C
1
-0.1 R
b
-1.0
R
2
-1.1 R
1
+0.1
R
3
+0.7 C
2
-0.1
C
3
-1.5 R
3
+0.1
R
4
-0.6 R
4
-0.1
R
5
+0.6 R
5
+0.1
Active filters are also sensitive to an op amp’s parameters
-Gain and Bandwidth, in particular. The LMV822/24 provide
a large gain and wide bandwidth. And DAAFs make excel-
lent use of these feature specifications.
Single Amplifier versions require a large open-loop to
closed-loop gain ratio - approximately 50 to 1, at the Fc of
the filter response.
Figure 12
shows an impressive photo-
graph of a network analyzer measurement (hp3577A). The
measurement was taken from a 300kHz version of
Figure
10
. At 300 kHz, the open-loop to closed-loop gain ratio @Fc
is about 5 to 1. This is 10 times lower than the 50 to 1 “rule
of thumb” for Single Amplifier Active Filters.
In addition to performance, DAAFs are relatively easy to
design and implement. The design equations for the low-
pass and high-pass DAAFs are shown below. The first two
equation calculate the Fc and the circuit Quality Factor (Q)
for the LPF (
Figure 10
). The second two equations calculate
the Fc and Q for the HPF (
Figure 11
).
To simplify the design process, certain components are set
equal to each other. Refer to
Figure 10
and
Figure 11
. These
equal component values help to simplify the design equa-
tions as follows:
To illustrate the design process/implementation, a 3 kHz,
Butterworth response, low-pass filter DAAF (
Figure 10
)is
designed as follows:
1. Choose C
1
=C
3
=C=1nF
2. Choose R
4
=R
5
=1kΩ
3. Calculate R
a
and R
2
for the desired Fc as follows:
DS100128-37
FIGURE 11. Dual Amplifier, 300 Hz High-Pass Active
Filter with a Butterworth Response and a Pass Band
Gain of Times Two
DS100128-92
FIGURE 12. 300 kHz, Low-Pass Filter, Butterworth
Response as Measured by the HP3577A Network
Analyzer
LMV821 Single/ LMV822 Dual/ LMV824 Quad
www.national.com 14
4. Calculate R
3
for the desired Q. The desired Q for a
Butterworth (Maximally Flat) response is 0.707 (45 degrees
into the s-plane). R
3
calculates as follows:
Notice that R
3
could also be calculated as 0.707 of R
a
or R
2.
The circuit was implemented and its cutoff frequency mea-
sured. The cutoff frequency measured at 2.92 kHz.
The circuit also showed good repeatability. Ten different
LMV822 samples were placed in the circuit. The correspond-
ing change in the cutoff frequency was less than a percent.
2.5 Tri-level Voltage Detector
The tri-level voltage detector of
Figure 13
provides a type of
window comparator function. It detects three different input
voltage ranges: Min-range, Mid-range, and Max-range. The
output voltage (V
O
)isatV
CC
for the Min-range. V
O
is
clamped at GND for the Mid-range. For the Max-range, V
O
is
at V
ee
.
Figure 14
shows a V
O
vs. V
I
oscilloscope photo per
the circuit of
Figure 13
.
Its operation is as follows: V
I
deviating from GND, causes
the diode bridge to absorb I
IN
to maintain a clamped condi-
tion (V
O
= 0V). Eventually, I
IN
reaches the bias limit of the
diode bridge. When this limit is reached, the clamping effect
stops and the op amp responds open loop. The design
equation directly preceding
Figure 14
, shows how to deter-
mine the clamping range. The equation solves for the input
voltage band on each side GND. The mid-range is twice this
voltage band.
DS100128-89
DS100128-34
FIGURE 13. Tri-level Voltage Detector
OV
-VIN +VIN
-Vo+Vo
OV
| ∆v | ∆v |
DS100128-35
FIGURE 14. X, Y Oscilloscope Trace showing V
OUT
vs
V
IN
per the Circuit of
Figure 13
LMV821 Single/ LMV822 Dual/ LMV824 Quad
www.national.com15
Connection Diagrams
Ordering Information
Package Temperature Range Packaging Marking Transport Media NSC DrawingIndustrial
−40˚C to +85˚C
5-Pin SC-70-5 LMV821M7 A15 1k Units Tape and Reel MAA05
LMV821M7X A15 3k Units Tape and Reel
5-Pin SOT23-5 LMV821M5 A14 1k UnitsTape and Reel MA05B
LMV821M5X A14 3k Units Tape and Reel
8-Pin SO LMV822M LMV822M Rails M08A
LMV822MX LMV822M 2.5k Units Tape and
Reel
8-Pin MSOP LMV822MM LMV822 1k Units Tape and Reel MUA08A
LMV822MMX LMV822 3.5k Units Tape and
Reel
14-Pin SO LMV824M LMV824M Rails M14A
LMV824MX LMV824M 2.5k Units Tape and
Reel
14-Pin TSSOP LMV824MT LMV824MT Rails MTC14
LMV824MTX LMV824MT 2.5k Units Tape and
Reel
5-Pin SC70-5/SOT23-5
DS100128-84
Top View
8-Pin SO/MSOP
DS100128-63
Top View
14-Pin SO/TSSOP
DS100128-85
Top View
LMV821 Single/ LMV822 Dual/ LMV824 Quad
www.national.com 16
SC70-5 Tape and Reel Specification
SOT-23-5 Tape and Reel Specification
Tape Format
Tape Section #Cavities Cavity Status Cover Tape Status
Leader 0 (min) Empty Sealed
(Start End) 75 (min) Empty Sealed
Carrier 3000 Filled Sealed
250 Filled Sealed
Trailer 125 (min) Empty Sealed
(Hub End) 0 (min) Empty Sealed
DS100128-96
LMV821 Single/ LMV822 Dual/ LMV824 Quad
www.national.com17
Tape Dimensions
8 mm 0.130 0.124 0.130 0.126 0.138 ±0.002 0.055 ±0.004 0.157 0.315 ±0.012
(3.3) (3.15) (3.3) (3.2) (3.5 ±0.05) (1.4 ±0.11) (4) (8 ±0.3)
Tape Size DIM A DIM Ao DIM B DIM Bo DIM F DIM Ko DIM P1 DIM W
DS100128-97
LMV821 Single/ LMV822 Dual/ LMV824 Quad
www.national.com 18
Reel Dimensions
8 mm 7.00 0.059 0.512 0.795 2.165 0.331 + 0.059/−0.000 0.567 W1+ 0.078/−0.039
330.00 1.50 13.00 20.20 55.00 8.40 + 1.50/−0.00 14.40 W1 + 2.00/−1.00
Tape Size A B C D N W1 W2 W3
DS100128-98
LMV821 Single/ LMV822 Dual/ LMV824 Quad
www.national.com19
Physical Dimensions inches (millimeters) unless otherwise noted
SC70-5
Order Number LMV821M7 or LMV821M7X
NS Package Number MAA05
SOT 23-5
Order Number LMV821M5 or LMV821M5X
NS Package Number MA05B
LMV821 Single/ LMV822 Dual/ LMV824 Quad
www.national.com 20
Physical Dimensions inches (millimeters) unless otherwise noted (Continued)
8-Pin Small Outline
Order Number LMV822M or LMV822MX
NS Package Number M08A
14-Pin Small Outline
Order Number LMV824M or LMV824MX
NS Package Number M14A
LMV821 Single/ LMV822 Dual/ LMV824 Quad
www.national.com21
Physical Dimensions inches (millimeters) unless otherwise noted (Continued)
8-Pin MSOP
Order Number LMV822MM or LMV822MMX
NS Package Number MUA08A
LMV821 Single/ LMV822 Dual/ LMV824 Quad
www.national.com 22
Physical Dimensions inches (millimeters) unless otherwise noted (Continued)
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DEVICES OR SYSTEMS WITHOUT THE EXPRESS WRITTEN APPROVAL OF THE PRESIDENT AND GENERAL
COUNSEL OF NATIONAL SEMICONDUCTOR CORPORATION. As used herein:
1. Life support devices or systems are devices or
systems which, (a) are intended for surgical implant
into the body, or (b) support or sustain life, and
whose failure to perform when properly used in
accordance with instructions for use provided in the
labeling, can be reasonably expected to result in a
significant injury to the user.
2. A critical component is any component of a life
support device or system whose failure to perform
can be reasonably expected to cause the failure of
the life support device or system, or to affect its
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Tel: 1-800-272-9959
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www.national.com
14-Pin TSSOP
Order Number LMV824MTC or LMV824MTCX
NS Package Number MTC14
LMV821 / LMV822 / LMV824 Single/Dual Quad Low Voltage, Low Power, RRO, 5 MHz Op Amps
National does not assume any responsibility for use of any circuitry described, no circuit patent licenses are implied and National reserves the right at any time without notice to change said circuitry and specifications.
