TI LMV821M5X

LMV821,LMV822,LMV824
LMV821 Single/ LMV822 Dual/ LMV824 Quad Low Voltage, Low Power, R-to-R
Output, 5 MHz Op Amps
Literature Number: SNOS032D
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. With a 5 MHz
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 Ω Guarantees). 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 economical price.
Features
Maximum VOS
3.5 mV (Guaranteed)
VOS Temp. Drift
1 uV/˚ C
GBW product @ 2.7 V
5 MHz
ISupply @ 2.7 V
220 µA/Amplifier
Minimum SR
1.4 V/us (Guaranteed)
CMRR
90 dB
PSRR
85 dB
VCM @ 5V
-0.3V to 4.3V
Rail-to-Rail (R-to-R) Output Swing
— @600 Ω Load
160 mV from rail
55 mV from rail
— @10 kΩ Load
n Stable with High Capacitive Loads (Refer to Application
Section)
n
n
n
n
n
n
n
n
n
Applications
n
n
n
n
n
Cordless Phones
Cellular Phones
Laptops
PDAs
PCMCIA
(For Typical, 5 V Supply Values; Unless Otherwise Noted)
n Ultra Tiny, SC70-5 Package
2.0 x 2.0 x 1.0 mm
n Guaranteed 2.5 V, 2.7 V and 5 V Performance
Telephone-line Transceiver for a
PCMCIA Modem Card
10012833
© 2003 National Semiconductor Corporation
DS100128
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LMV821 / LMV822 / LMV824 Single/Dual Quad Low Voltage, Low Power, RRO, 5 MHz Op Amps
November 2003
LMV821 Single/ LMV822 Dual/ LMV824 Quad
Absolute Maximum Ratings (Note 1)
Operating Ratings (Note 1)
If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales Office/
Distributors for availability and specifications.
Supply Voltage
Thermal Resistance (θ
100V
2000V
LMV821
Tiny SOT23-5 Package, 5-Pin
Surface Mount
1500V
Differential Input Voltage
± Supply Voltage
Supply Voltage (V+–V −)
5.5V
MSOP Package, 8-Pin Mini
Surface Mount
Output Short Circuit to V− (Note 3)
Infrared or Convection (20 sec)
Storage Temperature Range
Junction Temperature (Note 4)
235˚C
440 ˚C/W
190 ˚C/W
235 ˚C/W
SO Package, 14-Pin Surface
Mount
Soldering Information
≤85˚C
265 ˚C/W
SO Package, 8-Pin Surface Mount
Output Short Circuit to V+ (Note 3)
J
JA)
Ultra Tiny SC70-5 Package, 5-Pin
Surface Mount
Human Body Model
LMV822/824
−40˚C ≤T
LMV821, LMV822, LMV824
ESD Tolerance (Note 2)
Machine Model
2.5V to 5.5V
Temperature Range
145 ˚C/W
TSSOP Package, 14-Pin
155 ˚C/W
−65˚C to 150˚C
150˚C
2.7V DC Electrical Characteristics
Unless otherwise specified, all limits guaranteed for TJ = 25˚C. V+ = 2.7V, V
Boldface limits apply at the temperature extremes.
Symbol
VOS
Parameter
Condition
Input Offset Voltage
−
= 0V, VCM = 1.0V, VO = 1.35V and R
LMV821/822/824
Limit (Note 6)
1
3.5
mV
4
max
Input Offset Voltage Average
Drift
1
IB
Input Bias Current
30
IOS
Input Offset Current
0.5
+PSRR
−PSRR
VCM
Common Mode Rejection Ratio
0V ≤ VCM ≤ 1.7V
> 1 MΩ.
Typ
(Note 5)
TCVOS
CMRR
L
85
Positive Power Supply Rejection 1.7V ≤ V+ ≤ 4V, V- = 1V, VO =
Ratio
0V, VCM = 0V
85
Negative Power Supply
Rejection Ratio
-1.0V ≤ V- ≤ -3.3V, V+ = 1.7V,
VO = 0V, VCM = 0V
85
Input Common-Mode Voltage
Range
For CMRR ≥ 50dB
Units
µV/˚C
90
nA
140
max
30
nA
50
max
70
dB
68
min
75
dB
70
min
73
dB
70
min
-0.3
-0.2
V
2.0
1.9
max
V
min
AV
Large Signal Voltage Gain
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Sourcing, RL = 600Ω to 1.35V,
VO = 1.35V to 2.2V
100
Sinking, RL = 600Ω to 1.35V,
VO = 1.35V to 0.5V
90
Sourcing, RL = 2kΩ to 1.35V,
VO = 1.35V to 2.2V
100
Sinking, RL = 2kΩ to 1.35, VO =
1.35 to 0.5V
95
2
90
dB
85
min
85
dB
80
min
95
dB
90
min
90
dB
85
min
(Continued)
Unless otherwise specified, all limits guaranteed for TJ = 25˚C. V+ = 2.7V, V
Boldface limits apply at the temperature extremes.
Symbol
VO
Parameter
Output Swing
−
Condition
V+ = 2.7V, RL= 600Ω to 1.35V
V+ = 2.7V, RL= 2kΩ to 1.35V
= 0V, VCM = 1.0V, VO = 1.35V and R
Output Current
LMV821/822/824
Limit (Note 6)
Units
2.58
2.50
V
2.40
min
0.13
0.20
V
0.30
max
2.66
Sourcing, VO = 0V
> 1 MΩ.
Typ
(Note 5)
0.08
IO
L
16
2.60
V
2.50
min
0.120
V
0.200
max
12
mA
min
Sinking, VO = 2.7V
26
12
mA
0.22
0.3
mA
0.5
max
min
IS
Supply Current
LMV821 (Single)
LMV822 (Dual)
0.45
LMV824 (Quad)
0.72
0.6
mA
0.8
max
1.0
mA
1.2
max
2.5V DC Electrical Characteristics
Unless otherwise specified, all limits guaranteed for TJ = 25˚C. V+ = 2.5V, V
Boldface limits apply at the temperature extremes.
Symbol
Parameter
VOS
Input Offset Voltage
VO
Output Swing
−
Condition
V+ = 2.5V, RL = 600Ω to 1.25V
= 0V, VCM = 1.0V, VO = 1.25V and R
> 1 MΩ.
Typ
(Note 5)
LMV821/822/824
Limit (Note 6)
Units
1
3.5
mV
4
max
2.37
2.30
V
2.20
min
0.20
V
0.30
max
0.13
V+ = 2.5V, RL = 2kΩ to 1.25V
L
2.46
0.08
2.40
V
2.30
min
0.12
V
0.20
max
2.7V AC Electrical Characteristics
Unless otherwise specified, all limits guaranteed for TJ = 25˚C. V+ = 2.7V, V
Boldface limits apply at the temperature extremes.
Symbol
Parameter
Conditions
= 0V, VCM = 1.0V, VO = 1.35V and R
Typ
(Note 5)
LMV821/822/824 Limit
(Note 6)
L
> 1 MΩ.
Units
SR
Slew Rate
1.5
V/µs
GBW
Gain-Bandwdth Product
5
MHz
Φm
Phase Margin
61
Deg.
Gm
Gain Margin
en
(Note 7)
−
10
dB
Amp-to-Amp Isolation
(Note 8)
135
dB
Input-Related Voltage Noise
f = 1 kHz, VCM = 1V
28
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LMV821 Single/ LMV822 Dual/ LMV824 Quad
2.7V DC Electrical Characteristics
LMV821 Single/ LMV822 Dual/ LMV824 Quad
2.7V AC Electrical Characteristics
(Continued)
Unless otherwise specified, all limits guaranteed for TJ = 25˚C. V+ = 2.7V, V
Boldface limits apply at the temperature extremes.
Symbol
Parameter
Input-Referred Current Noise
f = 1 kHz
THD
Total Harmonic Distortion
f = 1 kHz, AV = −2,
RL = 10 kΩ, VO = 4.1 V
= 0V, VCM = 1.0V, VO = 1.35V and R
Typ
(Note 5)
Conditions
in
−
LMV821/822/824 Limit
(Note 6)
L
> 1 MΩ.
Units
0.1
0.01
%
PP
5V DC Electrical Characteristics
Unless otherwise specified, all limits guaranteed for TJ = 25˚C. V+ = 5V, V
Boldface limits apply at the temperature extremes.
Symbol
Parameter
−
Condition
= 0V, VCM = 2.0V, VO = 2.5V and R
LMV821/822/824
Limit (Note 6)
Units
3.5
mV
Input Offset Voltage
1
TCVOS
Input Offset Voltage Average
Drift
1
IB
Input Bias Current
40
4.0
Input Offset Current
0.5
0V ≤ VCM ≤ 4.0V
CMRR
Common Mode Rejection Ratio
+PSRR
Positive Power Supply Rejection 1.7V ≤ V+ ≤ 4V, V- = 1V, VO =
Ratio
0V, VCM = 0V
85
90
−PSRR
Negative Power Supply
Rejection Ratio
-1.0V ≤ V- ≤ -3.3V, V+ = 1.7V,
VO = 0V, VCM = 0V
VCM
Input Common-Mode Voltage
Range
For CMRR ≥ 50dB
> 1 MΩ.
Typ
(Note 5)
VOS
IOS
L
max
µV/˚C
100
nA
150
max
30
nA
50
max
72
dB
70
min
75
dB
70
min
85
73
dB
70
min
-0.3
-0.2
V
max
4.3
4.2
V
min
AV
VO
Large Signal Voltage Gain
Output Swing
Sourcing, RL = 600Ω to 2.5V,
VO = 2.5 to 4.5V
105
Sinking, RL = 600Ω to 2.5V, VO
= 2.5 to 0.5V
105
Sourcing, RL = 2kΩ to 2.5V, VO
= 2.5 to 4.5V
dB
90
min
95
dB
90
min
105
95
dB
90
min
Sinking, RL = 2kΩ to 2.5, VO =
2.5 to 0.5V
105
95
dB
90
min
V+ = 5V,RL = 600Ω to 2.5V
4.84
0.17
V+ = 5V, RL = 2kΩ to 2.5V
4.90
0.10
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95
4
4.75
V
4.70
min
0.250
V
.30
max
4.85
V
4.80
min
0.15
V
0.20
max
(Continued)
Unless otherwise specified, all limits guaranteed for TJ = 25˚C. V+ = 5V, V
Boldface limits apply at the temperature extremes.
Symbol
IS
Supply Current
= 0V, VCM = 2.0V, VO = 2.5V and R
L
> 1 MΩ.
Typ
(Note 5)
LMV821/822/824
Limit (Note 6)
Units
Sourcing, VO = 0V
45
20
mA
15
min
Sinking, VO = 5V
40
20
mA
15
min
Parameter
Output Current
IO
−
Condition
LMV821 (Single)
0.30
LMV822 (Dual)
0.5
LMV824 (Quad)
1.0
0.4
mA
0.6
max
0.7
mA
0.9
max
1.3
mA
1.5
max
5V AC Electrical Characteristics
Unless otherwise specified, all limits guaranteed for TJ = 25˚C. V+ = 5V, V
Boldface limits apply at the temperature extremes.
Symbol
Parameter
Conditions
−
= 0V, VCM = 2V, VO = 2.5V and R
L
> 1 MΩ.
Typ
(Note 5)
LMV821/822/824 Limit
(Note 6)
Units
2.0
1.4
V/µs min
SR
Slew Rate
GBW
Gain-Bandwdth Product
(Note 7)
5.6
MHz
Φm
Phase Margin
67
Deg.
Gm
Gain Margin
15
dB
dB
Amp-to-Amp Isolation
(Note 8)
135
en
Input-Related Voltage Noise
f = 1 kHz, VCM = 1V
24
in
Input-Referred Current Noise
f = 1 kHz
THD
Total Harmonic Distortion
f = 1 kHz, AV = −2,
RL = 10 kΩ, VO = 4.1 V
0.25
0.01
%
PP
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 kΩ in series wth 100 pF. Machine model, 200Ω in 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 = 100kΩ connected to 2.5V. Each amp excited in turn with 1 kHz to produce V O = 3 VPP.
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LMV821 Single/ LMV822 Dual/ LMV824 Quad
5V DC Electrical Characteristics
LMV821 Single/ LMV822 Dual/ LMV824 Quad
Typical Performance Characteristics
Unless otherwise specified, VS = +5V, single supply,
TA = 25˚C.
Supply Current vs. Supply Voltage (LMV821)
Input Current vs. Temperature
10012802
10012801
Sourcing Current vs. Output Voltage (VS = 2.7V)
Sourcing Current vs Output Voltage (VS = 5V)
10012803
10012804
Sinking Current vs. Output Voltage (VS = 2.7V)
Sinking Current vs. Output Voltage (VS = 5V)
10012805
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10012806
6
Output Voltage Swing vs. Supply Voltage (RL = 10kΩ)
Output Voltage Swing vs. Supply Voltage (RL = 2kΩ)
10012807
10012886
Output Voltage Swing vs. Supply Voltage (RL = 600Ω)
Output Voltage Swing vs. Load Resistance
10012808
10012887
Input Voltage Noise vs. Frequency
Input Current Noise vs. Frequency
10012818
10012817
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LMV821 Single/ LMV822 Dual/ LMV824 Quad
Typical Performance Characteristics Unless otherwise specified, VS = +5V, single supply,
TA = 25˚C. (Continued)
LMV821 Single/ LMV822 Dual/ LMV824 Quad
Typical Performance Characteristics Unless otherwise specified, VS = +5V, single supply,
TA = 25˚C. (Continued)
Crosstalk Rejection vs. Frequency
+PSRR vs. Frequency
10012809
10012893
-PSRR vs. Frequency
CMRR vs. Frequency
10012847
10012810
Gain and Phase Margin vs. Frequency
(RL = 100kΩ, 2kΩ, 600Ω) 2.7V
Input Voltage vs. Output Voltage
10012888
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10012811
8
Gain and Phase Margin vs. Frequency
(RL = 100kΩ, 2kΩ, 600Ω) 5V
Gain and Phase Margin vs. Frequency
(Temp.= 25, -40, 85˚C, RL = 10kΩ) 2.7V
10012812
10012813
Gain and Phase Margin vs. Frequency
(CL = 100pF, 200pF, 0pF, RL = 10kΩ)2.7V
Gain and Phase Margin vs. Frequency
(Temp.= 25, -40, 85 ˚C, RL = 10kΩ) 5V
10012814
10012815
Gain and Phase Margin vs. Frequency
(CL = 100pF, 200pF, 0pF RL = 600Ω) 2.7V
Gain and Phase Margin vs. Frequency
(CL = 100pF, 200pF, 0pF RL = 10kΩ) 5V
10012816
10012819
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LMV821 Single/ LMV822 Dual/ LMV824 Quad
Typical Performance Characteristics Unless otherwise specified, VS = +5V, single supply,
TA = 25˚C. (Continued)
LMV821 Single/ LMV822 Dual/ LMV824 Quad
Typical Performance Characteristics Unless otherwise specified, VS = +5V, single supply,
TA = 25˚C. (Continued)
Gain and Phase Margin vs. Frequency
(CL = 100pF, 200pF, 0pF RL = 600Ω) 5V
Slew Rate vs. Supply Voltage
10012862
10012820
Non-Inverting Large Signal Pulse Response
Non-Inverting Small Signal Pulse Response
10012821
10012824
Inverting Large Signal Pulse Response
Inverting Small Signal Pulse Response
10012827
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10012830
10
LMV821 Single/ LMV822 Dual/ LMV824 Quad
Typical Performance Characteristics Unless otherwise specified, VS = +5V, single supply,
TA = 25˚C. (Continued)
THD vs. Frequency
10012882
added in parallel with 220 picofarads capacitance, to increase the φm 20˚(approx.), but at the price of about a 100
kHz of bandwidth.
Application Note
This application note is divided into two sections: design
considerations and Application Circuits.
Overall, the LMV821/822/824 family provides good stability
for loaded condition.
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
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 (φm) specifies this output-to-input phase relationship
at the unity-gain crossover point. Zero degrees of phasemargin 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 φm for a no load condition. But φm
changes with load. The Gain and Phase margin vs Frequency plots in the curve section can be used to graphically
determine the φm 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 φm and the bandwidth of the LMV821/822/824
family. These graphs show capacitive loads reducing both
φm and bandwidth, while resistive loads reduce the bandwidth but increase the φm. Notice how a 600Ω resistor can be
10012860
FIGURE 1. Phase Margin vs Common Mode Voltage for
Various Loads
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LMV821 Single/ LMV822 Dual/ LMV824 Quad
Application Note
(Continued)
10012854
FIGURE 5. Pulse Response per Figure 4
10012861
INPUT BIAS CURRENT CONSIDERATION
Input bias current (IB) can develop a somewhat significant
offset voltage. This offset is primarily due to IB flowing
through the negative feedback resistor, RF. For example, if IB
is 90 nA (max @ room) and RF is 100 kΩ, then an offset of 9
mV will be developed (VOS=IBx RF).Using a compensation
resistor (RC), as shown in Figure 6, cancels out this affect.
But the input offset current (IOS) will still contribute to an
offset voltage in the same manner - typically 0.05 mV at
room temp.
FIGURE 2. Unity-Gain Frequency vs Common Mode
Voltage for Various Loads
UNITY GAIN PULSE RESPONSE CONSIDERATION
A pull-up resistor is well suited for increasing unity-gain,
pulse response stability. For example, a 600 Ω pull-up resistor 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.
10012841
FIGURE 3. Using a Pull-up Resistor at the Output for
Stabilizing Capacitive Loads
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 approach is to use an isolation resistor as illustrated in Figure 4
.
Figure 5 shows the resulting pulse response from a LMV824,
while driving a 10,000 pF load through a 20Ω isolation
resistor.
10012859
FIGURE 6. Canceling the Voltage Offset Effect of Input
Bias Current
APPLICATION CIRCUITS
This section covers the following application circuits:
1. Telephone-Line Transceiver
2. “Simple” Mixer (Amplitude Modulator)
10012843
FIGURE 4. Using an Isolation Resistor to Drive Heavy
Capacitive Loads
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(Continued)
3. Dual Amplifier Active Filters (DAAFs)
a. Low-Pass Filter (LPF)
•
b. High-Pass Filter (HPF)
•
4. Tri-level Voltage Detector
TELEPHONE-LINE TRANSCEIVER
The telephone-line transceiver of Figure 7 provides a fullduplexed connection through a PCMCIA, miniature transformer. 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
Rmatch is chosen to match the coupled telephone-line impedance; therefore dividing VT by two (assuming R1 >>
Rmatch). The differential configuration of UR has its resistors
chosen to cancel the VT and VT/2 inputs according to the
following equation:
10012839
FIGURE 8. Amplitude Modulator Circuit
f
mod
f
carrier
10012840
FIGURE 9. Output signal per the Circuit of Figure 8
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 amplifier 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.
10012833
FIGURE 7. Telephone-line Transceiver for a PCMCIA
Modem Card
Note that Cr is included for canceling out the inadequacies of
the lossy, miniature transformer. Refer to application note
AN-397 for detailed explanation.
“SIMPLE” MIXER (AMPLITUDE MODULATOR)
The mixer of Figure 8 is simple and provides a unique form
of amplitude modulation. Vi is the modulation frequency
(FM), while a +3V square-wave at the gate of Q1, induces a
carrier frequency (FC). Q1 switches (toggles) U1 between
inverting and non-inverting unity gain configurations. Offsetting a sine wave above ground at Vi results in the oscilloscope 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 components. This difference frequency magnitude (/FM-FC/) is the
key factor for determining an object’s velocity per the Doppler Effect. If a signal is transmitted to a moving object, the
reflected frequency will be a different frequency. This difference in transmit and receive frequency is directly proportional to an object’s velocity.
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LMV821 Single/ LMV822 Dual/ LMV824 Quad
Application Note
LMV821 Single/ LMV822 Dual/ LMV824 Quad
Application Note
Note that this information provides insight on how to fine
tune the cutoff frequency, if necessary. It should be also
noted that R4 and R5 of each circuit also caused variations in
the pass band gain. Increasing R4 by ten percent, increased
the gain by 0.4 dB, while increasing R5 by ten percent,
decreased the gain by 0.4 dB.
(Continued)
TABLE 1.
10012836
Component
(LPF)
Sensitivity
(LPF)
Component
(HPF)
Sensitivity
(HPF)
-0.7
Ra
-1.2
Ca
C1
-0.1
Rb
-1.0
R2
-1.1
R1
+0.1
R3
+0.7
C2
-0.1
C3
-1.5
R3
+0.1
R4
-0.6
R4
-0.1
R5
+0.6
R5
+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 excellent 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 photograph of a network analyzer measurement (hp3577A). The
measurement was taken from a 300 kHz 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.
FIGURE 10. Dual Amplifier, 3 kHz Low-Pass Active
Filter with a Butterworth Response and a Pass Band
Gain of Times Two
10012837
FIGURE 11. Dual Amplifier, 300 Hz High-Pass Active
Filter with a Butterworth Response and a Pass Band
Gain of Times Two
10012892
FIGURE 12. 300 kHz, Low-Pass Filter, Butterworth
Response as Measured by the HP3577A Network
Analyzer
Table 1 provides sensitivity measurements for a 10 MΩ load
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 respective 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 relative 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.
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In addition to performance, DAAFs are relatively easy to
design and implement. The design equations for the lowpass 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).
14
(Continued)
Notice that R3 could also be calculated as 0.707 of Ra or R2.
The circuit was implemented and its cutoff frequency measured. The cutoff frequency measured at 2.92 kHz.
The circuit also showed good repeatability. Ten different
LMV822 samples were placed in the circuit. The corresponding change in the cutoff frequency was less than a percent.
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 equations as follows:
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 (VO) is at VCC for the Min-range. VO is
clamped at GND for the Mid-range. For the Max-range, VO is
at Vee. Figure 14 shows a VO vs. VI oscilloscope photo per
the circuit of Figure 13.
Its operation is as follows: VI deviating from GND, causes
the diode bridge to absorb IIN to maintain a clamped condition (VO= 0V). Eventually, IIN 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 determine the clamping range. The equation solves for the input
voltage band on each side GND. The mid-range is twice this
voltage band.
To illustrate the design process/implementation, a 3 kHz,
Butterworth response, low-pass filter DAAF (Figure 10) is
designed as follows:
1. Choose C1 = C3 = C = 1 nF
2. Choose R4 = R5 = 1 kΩ
3. Calculate Ra and R2 for the desired Fc as follows:
10012889
4. Calculate R3 for the desired Q. The desired Q for a
Butterworth (Maximally Flat) response is 0.707 (45 degrees
into the s-plane). R3 calculates as follows:
15
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LMV821 Single/ LMV822 Dual/ LMV824 Quad
Application Note
(Continued)
10012834
FIGURE 13. Tri-level Voltage Detector
∆v
|
∆v
|
+Vo
|
OV
-Vo
LMV821 Single/ LMV822 Dual/ LMV824 Quad
Application Note
-VIN
OV
+VIN
10012835
FIGURE 14. X, Y Oscilloscope Trace showing VOUT vs VIN per the Circuit of Figure 13
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16
5-Pin SC70-5/SOT23-5
8-Pin SO/MSOP
14-Pin SO/TSSOP
10012884
Top View
10012863
10012885
Top View
Top View
Ordering Information
Temperature Range
Package
Industrial
Packaging Marking
Transport Media
NSC Drawing
A15
1k Units Tape and Reel
MAA05
−40˚C to +85˚C
5-Pin SC-70-5
LMV821M7
LMV821M7X
5-Pin SOT23-5
LMV821M5
3k Units Tape and Reel
A14
LMV821M5X
8-Pin SOIC
LMV822M
LMV822M
LMV822MX
8-Pin MSOP
LMV822MM
LMV824M
LMV822
LMV824MT
Rails
M08A
1k Units Tape and Reel
MUA08A
3.5k Units Tape and
Reel
LMV824M
LMV824MX
14-Pin TSSOP
MF05A
2.5k Units Tape and
Reel
LMV822MMX
14-Pin SOIC
1k UnitsTape and Reel
3k Units Tape and Reel
Rails
M14A
2.5k Units Tape and
Reel
LMV824MT
LMV824MTX
Rails
MTC14
2.5k Units Tape and
Reel
17
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LMV821 Single/ LMV822 Dual/ LMV824 Quad
Connection Diagrams
LMV821 Single/ LMV822 Dual/ LMV824 Quad
SC70-5 Tape and Reel
Specification
10012896
SOT-23-5 Tape and Reel
Specification
Tape Format
www.national.com
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
18
LMV821 Single/ LMV822 Dual/ LMV824 Quad
Tape Dimensions
10012897
8 mm
Tape Size
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)
DIM A
DIM Ao
DIM B
DIM Bo
DIM F
DIM Ko
DIM P1
DIM W
19
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LMV821 Single/ LMV822 Dual/ LMV824 Quad
Reel Dimensions
10012898
8 mm
Tape Size
www.national.com
7.00
0.059 0.512 0.795 2.165
330.00
1.50
A
B
13.00 20.20 55.00
C
D
N
20
0.331 + 0.059/−0.000
0.567
W1+ 0.078/−0.039
8.40 + 1.50/−0.00
14.40
W1 + 2.00/−1.00
W1
W2
W3
LMV821 Single/ LMV822 Dual/ LMV824 Quad
Physical Dimensions
inches (millimeters) unless otherwise noted
SC70-5
NS Package Number MAA05
SOT 23-5
NS Package Number MF05A
21
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LMV821 Single/ LMV822 Dual/ LMV824 Quad
Physical Dimensions
inches (millimeters) unless otherwise noted (Continued)
8-Pin Small Outline
NS Package Number M08A
14-Pin Small Outline
NS Package Number M14A
www.national.com
22
LMV821 Single/ LMV822 Dual/ LMV824 Quad
Physical Dimensions
inches (millimeters) unless otherwise noted (Continued)
8-Pin MSOP
NS Package Number MUA08A
14-Pin TSSOP
NS Package Number MTC14
23
www.national.com
LMV821 / LMV822 / LMV824 Single/Dual Quad Low Voltage, Low Power, RRO, 5 MHz Op Amps
Notes
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NATIONAL’S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT
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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Stewardship Specification (CSP-9-111C2) and the Banned Substances and Materials of Interest Specification
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Email: [email protected]
Tel: 1-800-272-9959
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Fax: +49 (0) 180-530 85 86
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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.
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