NSC LMV824 Low voltage, low power, r-to-r output, 5 mhz op amp Datasheet

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
(For Typical, 5 V Supply Values; Unless Otherwise Noted)
n Ultra Tiny, SC70-5 Package
2.0 x 2.0 x 1.0 mm
Guaranteed 2.5 V, 2.7 V and 5 V Performance
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
Rail-to-Rail (R-to-R) Output Swing
— @600 Ω Load
160 mV from rail
— @10 kΩ Load
55 mV from rail
n VCM @ 5 V
-0.3 V to 4.3 V
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
Connection Diagrams
5-Pin SC70-5/SOT23-5
14-Pin SO/TSSOP
DS100128-84
Top View
8-Pin SO/MSOP
DS100128-85
Top View
DS100128-63
Top View
© 1999 National Semiconductor Corporation
DS100128
www.national.com
LMV821 Single/ LMV822 Dual/ LMV824 Quad Low Voltage, Low Power, RRO, 5 MHz Op Amps
August 1999
Ordering Information
Temperature Range
Package
Industrial
Packaging Marking
Transport Media
NSC Drawing
MAA05
−40˚C to +85˚C
5-Pin SC-70-5
5-Pin SOT23-5
8-Pin SO
8-Pin MSOP
14-Pin SO
14-Pin TSSOP
www.national.com
LMV821M7
A15
1k Units Tape and Reel
LMV821M7X
A15
3k Units Tape and Reel
LMV821M5
A14
1k UnitsTape and Reel
LMV821M5X
A14
3k Units Tape and Reel
LMV822M
LMV822M
Rails
LMV822MX
LMV822M
2.5k Units Tape and
Reel
LMV822MM
LMV822
1k Units Tape and Reel
LMV822MMX
LMV822
3.5k Units Tape and
Reel
LMV824M
LMV824M
Rails
LMV824MX
LMV824M
2.5k Units Tape and
Reel
LMV824MT
LMV824MT
Rails
LMV824MTX
LMV824MT
2.5k Units Tape and
Reel
2
MA05B
M08A
MUA08A
M14A
MTC14
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
2.5V to 5.5V
Temperature Range
−40˚C ≤T
LMV821, LMV822, LMV824
ESD Tolerance (Note 2)
Machine Model
Thermal Resistance (θ
100V
Ultra Tiny SC70-5 Package
5-Pin Surface Mount
Human Body Model
LMV822/824
2000V
LMV821
1500V
Differential Input Voltage
± Supply Voltage
Supply Voltage (V+–V −)
5.5V
Tiny SOT23-5 Package
Surface Mount
Output Short Circuit to V+ (Note 3)
Output Short Circuit to V− (Note 3)
Storage Temperature Range
Junction Temperature (Note 4)
≤85˚C
440 ˚C/W
5-Pin
265 ˚C/W
SO Package, 8-Pin Surface
Mount
190 ˚C/W
MSOP Package, 8-Pin Mini
Surface
Mount
235 ˚C/W
Soldering Information
Infrared or Convection (20 sec)
J
JA)
235˚C
−65˚C to 150˚C
SO Package, 14-Pin Surface
Mount
145 ˚C/W
TSSOP Package, 14-Pin
155 ˚C/W
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
CMRR
+PSRR
−PSRR
VCM
Input Offset Current
Common Mode Rejection Ratio
0.5
0V ≤ VCM ≤ 1.7V
> 1 MΩ.
Typ
(Note 5)
TCVOS
IOS
L
85
Positive Power Supply
Rejection Ratio
1.7V ≤ V+ ≤ 4V, V- = 1V, VO =
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
-0.3
Units
µV/˚C
90
nA
140
max
30
nA
50
max
70
dB
68
min
75
dB
70
min
73
dB
70
min
-0.2
V
max
2.0
1.9
V
min
AV
Large Signal Voltage Gain
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
3
90
dB
85
min
85
dB
80
min
95
dB
90
min
90
dB
85
min
www.national.com
2.7V DC 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
VO
Parameter
Output Swing
−
Condition
+
V =2.7V, RL= 600Ω to 1.35V
= 0V, VCM = 1.0V, VO = 1.35V and R
LMV821/822/824
Limit (Note 6)
2.58
2.50
V
2.40
min
2.66
0.08
IO
Output Current
Sourcing, VO=0V
> 1 MΩ.
Typ
(Note 5)
0.13
V+=2.7V, RL= 2kΩ to 1.35V
L
16
Units
0.20
V
0.30
max
2.60
V
2.50
min
0.120
V
0.200
max
12
mA
min
Sinking, VO=2.7V
26
12
mA
min
IS
Supply Current
LMV821 (Single)
0.22
LMV822 (Dual)
0.45
LMV824 (Quad)
0.72
0.3
mA
0.5
max
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
VOS
VO
Parameter
−
Condition
Input Offset Voltage
Output Swing
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)
1
3.5
mV
4
max
2.37
0.13
V+=2.5V, RL= 2kΩ to 1.25V
L
2.46
0.08
Units
2.30
V
2.20
min
0.20
V
0.30
max
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
SR
Slew Rate
GBW
Conditions
= 0V, VCM = 1.0V, VO = 1.35V and R
Typ
(Note 5)
L
LMV821/822/824 Limit
(Note 6)
> 1 MΩ.
Units
1.5
V/µs
Gain-Bandwdth Product
5
MHz
Φm
Phase Margin
61
Deg.
Gm
Gain Margin
10
dB
dB
en
(Note 7)
−
Amp-to-Amp Isolation
(Note 8)
135
Input-Related Voltage Noise
f = 1 kHz, VCM = 1V
28
www.national.com
4
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
−
= 0V, VCM = 1.0V, VO = 1.35V and R
Typ
(Note 5)
Conditions
in
Input-Referred Current Noise
f = 1 kHz
0.1
THD
Total Harmonic Distortion
f = 1 kHz, AV = −2,
RL = 10 kΩ, VO = 4.1 VPP
0.01
L
LMV821/822/824 Limit
(Note 6)
> 1 MΩ.
Units
%
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
VOS
Parameter
−
Condition
Input Offset Voltage
= 0V, VCM = 2.0V, VO = 2.5V and R
LMV821/822/824
Limit (Note 6)
1
3.5
mV
4.0
max
Input Offset Voltage Average
Drift
1
IB
Input Bias Current
40
CMRR
+PSRR
−PSRR
VCM
Input Offset Current
Common Mode Rejection Ratio
0.5
0V ≤ VCM ≤ 4.0V
> 1 MΩ.
Typ
(Note 5)
TCVOS
IOS
L
90
Positive Power Supply
Rejection Ratio
1.7V ≤ V+ ≤ 4V, V- = 1V, VO =
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
-0.3
Units
µV/˚C
100
nA
150
max
30
nA
50
max
72
dB
70
min
75
dB
70
min
73
dB
70
min
-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
105
Sinking, RL=2kΩ to 2.5,
VO=2.5 to 0.5V
105
V+=5V,RL= 600Ω to 2.5V
4.84
0.17
V+=5V, RL=2kΩ to 2.5V
4.90
0.10
5
95
dB
90
min
95
dB
90
min
95
dB
90
min
95
dB
90
min
4.75
V
4.70
min
0.250
V
.30
max
4.85
V
4.80
min
0.15
V
0.20
max
www.national.com
5V DC Electrical Characteristics
(Continued)
Unless otherwise specified, all limits guaranteed for TJ = 25˚C. V+ = 5V, V
Boldface limits apply at the temperature extremes.
Symbol
IO
Parameter
Output Current
−
= 0V, VCM = 2.0V, VO = 2.5V and R
Typ
(Note 5)
Condition
Sourcing, VO=0V
IS
Supply Current
40
LMV821 (Single)
0.30
LMV822 (Dual)
0.5
LMV824 (Quad)
> 1 MΩ.
LMV821/822/824
Limit (Note 6)
45
Sinking, VO=5V
L
1.0
Units
20
mA
15
min
20
mA
15
min
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)
2.0
1.4
(Note 7)
Units
SR
Slew Rate
V/µs
min
GBW
Gain-Bandwdth Product
5.6
MHz
Φm
Phase Margin
67
Deg.
Gm
Gain Margin
15
dB
Amp-to-Amp Isolation
(Note 8)
135
dB
en
Input-Related Voltage Noise
f = 1 kHz, VCM = 1V
24
in
Input-Referred Current Noise
f = 1 kHz
0.25
THD
Total Harmonic Distortion
f = 1 kHz, AV = −2,
RL = 10 kΩ, VO = 4.1 VPP
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 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 = (TJAll numbers apply for packages soldered directly into a PC board.
(max)–T A)/θJA.
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 = 100 kΩ connected to 2.5V. Each amp excited in turn with 1 kHz to produce V O = 3 VPP.
www.national.com
6
5V AC Electrical Characteristics
(Continued)
Typical Performance Characteristics
Supply Current vs Supply Voltage
(LMV821)
Unless otherwise specified, VS = +5V, single supply, TA = 25˚C.
Input Current vs Temperature
Sourcing Current vs Output
Voltage (VS=2.7V)
DS100128-2
DS100128-1
Sourcing Current vs Output
Voltage (VS=5V)
DS100128-3
Sinking Current vs Output Voltage
(VS=2.7V)
DS100128-4
Output Voltage Swing vs Supply
Voltage (RL=10kΩ)
DS100128-5
Output Voltage Swing vs Supply
Voltage (RL=2kΩ)
DS100128-7
DS100128-86
7
Sinking Current vs Output Voltage
(VS=5V)
DS100128-6
Output Voltage Swing vs Supply
Voltage (RL=600Ω)
DS100128-8
www.national.com
Typical Performance Characteristics
Unless otherwise specified, VS = +5V, single supply,
TA = 25˚C. (Continued)
Output Voltage Swing vs Load
Resistance
Input Voltage Noise vs Frequency
Input Current Noise vs Frequency
DS100128-18
DS100128-17
DS100128-87
Crosstalk Rejection vs Frequency
+PSRR vs Frequency
DS100128-93
CMRR vs Frequency
-PSRR vs Frequency
DS100128-9
Input Voltage vs Output Voltage
DS100128-10
Gain and Phase Margin vs
Frequency (RL=100kΩ, 2kΩ, 600Ω)
2.7V
DS100128-88
DS100128-47
DS100128-11
www.national.com
8
Typical Performance Characteristics
Unless otherwise specified, VS = +5V, single supply,
TA = 25˚C. (Continued)
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
Gain and Phase Margin vs
Frequency (Temp.=25, -40, 85 ˚C,
RL=10kΩ) 5V
DS100128-12
DS100128-13
DS100128-14
Gain and Phase Margin vs
Frequency (CL=100pF, 200pF, 0pF,
RL=10kΩ)2.7V
Gain and Phase Margin vs
Frequency (CL=100pF,200pF,0pF
RL=10kΩ)5V
Gain and Phase Margin vs
Frequency (CL=100pF,200pF,0pF
RL=600Ω)2.7V
DS100128-15
DS100128-16
DS100128-19
Gain and Phase Margin vs
Frequency (CL=100pF,200pF,0pF
RL=600Ω)5V
Slew Rate vs Supply Voltage
DS100128-62
Non-Inverting Large Signal Pulse
Response
DS100128-21
DS100128-20
9
www.national.com
Typical Performance Characteristics
Unless otherwise specified, VS = +5V, single supply,
TA = 25˚C. (Continued)
Non-Inverting Small Signal Pulse
Response
Inverting Large Signal Pulse
Response
DS100128-24
DS100128-27
THD vs Frequency
DS100128-82
www.national.com
10
Inverting Small Signal Pulse
Response
DS100128-30
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 (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 unitygain 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 added in
parallel with 220 picofarads capacitance, to increase the φm
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.
DS100128-61
FIGURE 2. Unity-Gain Frequency vs Common Mode
Voltage for Various Loads
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 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.
DS100128-41
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 10,000pF load through a 20 Ω isolation
resistor.
DS100128-43
FIGURE 4. Using an Isolation Resistor to Drive Heavy
Capacitive Loads
DS100128-60
FIGURE 1. Phase Margin vs Common Mode Voltage for
Various Loads
11
www.national.com
2.1 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:
DS100128-54
FIGURE 5. Pulse Response per Figure 4
1.3 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 90nA (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.
DS100128-33
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.
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
(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.
DS100128-59
FIGURE 6. Canceling the Voltage Offset Effect of Input
Bias Current
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
www.national.com
12
DS100128-39
FIGURE 8. Amplitude Modulator Circuit
DS100128-36
FIGURE 10. Dual Amplifier, 3 kHz Low-Pass Active
Filter with a Butterworth Response and a Pass Band
Gain of Times Two
f
mod
f
carrier
DS100128-40
FIGURE 9. Output signal per the Circuit of Figure 8
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 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.
DS100128-37
FIGURE 11. Dual Amplifier, 300 Hz High-Pass Active
Filter with a Butterworth Response and a Pass Band
Gain of Times Two
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.
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
13
www.national.com
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.
TABLE 1.
Component (LPF)
Sensitivity (LPF)
Component (HPF)
Sensitivity (HPF)
Ra
-1.2
Ca
-0.7
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 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.
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:
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:
DS100128-92
FIGURE 12. 300 kHz, Low-Pass Filter, Butterworth
Response as Measured by the HP3577A Network
Analyzer
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:
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).
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.
www.national.com
14
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.
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 (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
DS100128-89
∆v
|
∆v
|
+Vo
|
-Vo
OV
-VIN
OV
+VIN
DS100128-35
FIGURE 14. X, Y Oscilloscope Trace showing VOUT vs
VIN per the Circuit of Figure 13
DS100128-34
FIGURE 13. Tri-level Voltage Detector
15
www.national.com
SC70-5 Tape and Reel Specification
DS100128-96
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
16
Tape Dimensions
DS100128-97
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
17
www.national.com
Reel Dimensions
DS100128-98
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
18
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
Physical Dimensions
inches (millimeters) unless otherwise noted
SC70-5
Order Number LMV821M7 or LMV821M7X
NS Package Number MAA05
19
www.national.com
Physical Dimensions
inches (millimeters) unless otherwise noted (Continued)
SOT 23-5
Order Number LMV821M5 or LMV821M5X
NS Package Number MA05B
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
21
www.national.com
Physical Dimensions
inches (millimeters) unless otherwise noted (Continued)
8-Pin MSOP
Order Number LMV822MM or LMV822MMX
NS Package Number MUA08A
www.national.com
22
Physical Dimensions
inches (millimeters) unless otherwise noted (Continued)
14-Pin Small Outline
Order Number LMV824M or LMV824MX
NS Package Number M14A
23
www.national.com
LMV821 Single/ LMV822 Dual/ LMV824 Quad Low Voltage, Low Power, RRO, 5 MHz Op Amps
Physical Dimensions
inches (millimeters) unless otherwise noted (Continued)
14-Pin TSSOP
Order Number LMV824MTC or LMV824MTCX
NS Package Number MTC14
LIFE SUPPORT POLICY
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.
National Semiconductor
Corporation
Americas
Tel: 1-800-272-9959
Fax: 1-800-737-7018
Email: [email protected]
www.national.com
National Semiconductor
Europe
Fax: +49 (0) 1 80-530 85 86
Email: [email protected]
Deutsch Tel: +49 (0) 1 80-530 85 85
English Tel: +49 (0) 1 80-532 78 32
Français Tel: +49 (0) 1 80-532 93 58
Italiano Tel: +49 (0) 1 80-534 16 80
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
safety or effectiveness.
National Semiconductor
Asia Pacific Customer
Response Group
Tel: 65-2544466
Fax: 65-2504466
Email: [email protected]
National Semiconductor
Japan Ltd.
Tel: 81-3-5639-7560
Fax: 81-3-5639-7507
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.