LM321
LM321 Low Power Single Op Amp
FEATURES
DESCRIPTION
•
The LM321 brings performance and economy to low
power systems. With a high unity gain frequency and
a specified 0.4V/µs slew rate, the quiescent current is
only 430µA/amplifier (5V). The input common mode
range includes ground and therefore the device is
able to operate in single supply applications as well
as in dual supply applications. It is also capable of
comfortably driving large capacitive loads.
1
2
•
•
•
•
•
•
(VCC = 5V, TA = 25°C. Typical values unless
specified.)
Gain-Bandwidth Product 1MHz
Low Supply Current 430µA
Low Input Bias Current 45nA
Wide Supply Voltage Range +3V to +32V
Stable With High Capacitive Loads
Single Version of LM324
The LM321 is available in the SOT-23 package.
Overall the LM321 is a low power, wide supply range
performance op amp that can be designed into a
wide range of applications at an economical price
without sacrificing valuable board space.
APPLICATIONS
•
•
•
•
•
Chargers
Power Supplies
Industrial: Controls, Instruments
Desktops
Communications Infrastructure
Connection Diagram
Application Circuit
SOT-23
DC Summing Amplifier
(VIN's ≥ 0 VDC and VO ≥ VDC)
Top View
Where: V0 = V1 + V2 - V3 - V4, (V1+V2) ≥
(V3 + V4) to keep VO > 0 VDC
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LM321
These devices have limited built-in ESD protection. The leads should be shorted together or the device placed in conductive foam
during storage or handling to prevent electrostatic damage to the MOS gates.
Absolute Maximum Ratings
(1)
Differential Input Voltage
Input Current (VIN < −0.3V)
±Supply Voltage
(2)
50mA
Supply Voltage (V+ - V−)
32V
−0.3V to +32V
Input Voltage
Output Short Circuit to GND,
V+ ≤ 15V and TA = 25°C (3)
Continuous
Storage Temperature Range
−65°C to 150°C
Junction Temperature
(4)
150°C
Mounting Temperature
Lead Temp (Soldering, 10 sec)
260°C
Infrared (10 sec)
215°C
Thermal Resistance to Ambient (θJA)
ESD Tolerance
(1)
(2)
(3)
(4)
(5)
265°C/W
(5)
300V
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 ensured. For ensured specifications and the test
conditions, see the Electrical Characteristics.
This input current will only exist when the voltage at any of the input leads is driven negative. It is due to the collector base junction of
the input PNP transistors becoming forward biased and thereby acting as input diode clamps. In addition to this diode action, there is
also lateral NPN parasitic transistor action on the IC chip. This transistor action can cause the output voltages of the op amps to go to
the V+ voltage level (or to ground for a large overdrive) for the time duration that an input is driven negative. This is not destructive and
normal output states will re-establish when the input voltage, which was negative, again returns to a value greater than −0.36V (at
25°C).
Short circuits from the output V+ can cause excessive heating and eventual destruction. When considering short circuits to ground the
maximum output current is approximately 40mA independent of the magnitude of V+. At values of supply voltage in excess of +15V,
continuous short circuits can exceed the power dissipation ratings and cause eventual destruction.
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) - TA)/ θJA. All numbers apply for packages soldered directly onto a PC board.
Human Body Model, 1.5kΩ in series with 100pF.
Operating Ratings
(1)
−40°C to 85°C
Temperature Range
Supply Voltage
(1)
3V to 30V
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 ensured. For ensured specifications and the test
conditions, see the Electrical Characteristics.
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Electrical Characteristics
Unless otherwise specified, all limits specified for at TA = 25°C; V+ = 5V, V− = 0V, VO = 1.4V. Boldface limits apply at
temperature extremes.
Symbol
Parameter
Conditions
Min
(1)
(3)
Typ
Max
Units
2
7
9
mV
5
50
150
nA
45
250
500
nA
V+ - 1.5
V+ -2
V
(2)
(1)
VOS
Input Offset Voltage
IOS
Input Offset Current
IB
Input Bias Current
VCM
Input Common-Mode Voltage Range
V+ = 30V (5)
For CMRR > = 50dB
0
AV
Large Signal Voltage Gain
(V+ = 15V, RL = 2kΩ
VO = 1.4V to 11.4V)
25
15
100
V/mV
PSRR
Power Supply Rejection Ratio
RS ≤ 10kΩ,
V+ ≤ 5V to 30V
65
100
dB
CMRR
Common Mode Rejection Ratio
RS ≤ 10kΩ
65
85
dB
VO
(4)
Output Swing
VOH
VOL
IS
Supply Current, No Load
+
V = 30V, RL = 2kΩ
26
V+ = 30V, RL = 10kΩ
27
V+ = 5V, RL = 10kΩ
V
28
5
20
mV
V = 5V
0.430
0.7
1.15
1.2
mA
V+ = 30V
0.660
1.5
2.85
3
+
ISOURCE
Output Current Sourcing
VID = +1V, V+ = 15V,
VO = 2V
20
10
40
20
ISINK
Output Current Sinking
VID = −1V
V+ = 15V, VO = 2V
10
5
20
8
VID = −1V
V+ = 15V, VO = 0.2V
12
100
mA
mA
µA
IO
Output Short Circuit to Ground
V+ = 15V
40
SR
Slew Rate
V+ = 15V, RL = 2kΩ,
VIN = 0.5 to 3V
CL = 100pF, Unity Gain
0.4
V/µs
V+ = 30V, f = 100kHz,
VIN = 10mV, RL =2kΩ,
CL = 100pF
1
MHz
60
deg
0.015
%
(6)
GBW
Gain Bandwidth Product
φm
Phase Margin
THD
Total Harmonic Distortion
en
(1)
(2)
(3)
(4)
(5)
(6)
Equivalent Input Noise Voltage
f = 1kHz, AV = 20dB
RL = 2kΩ, VO = 2VPP,
CL = 100pF, V+ = 30V
f = 1kHz, RS = 100Ω
V+ = 30V
40
85
mA
nV/
All limits are specified by testing or statistical analysis.
Typical values represent the most likely parametric norm.
VO ≅ 1.4V, RS = 0Ω with V+ from 5V to 30V; and over the full input common-mode range (0V to V+ - 1.5V) at 25°C.
The direction of the input current is out of the IC due to the PNP input stage. This current is essentially constant, independent of the
state of the output so no loading change exists on the input lines.
The input common-mode voltage of either input signal voltage should not be allowed to go negative by more than 0.3V (at 25°C). The
upper end of the common-mode voltage range is V+ - 1.5V at 25°C, but either or both inputs can go to +32V without damage,
independent of the magnitude of V+.
Short circuits from the output V+ can cause excessive heating and eventual destruction. When considering short circuits to ground the
maximum output current is approximately 40mA independent of the magnitude of V+. At values of supply voltage in excess of +15V,
continuous short circuits can exceed the power dissipation ratings and cause eventual destruction.
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Simplified Schematic
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Typical Performance Characteristics
Unless otherwise specified, VS = +5V, single supply, TA = 25°C.
Small Signal Pulse Response
Large Signal Pulse Response
Supply Current
vs.
Supply Voltage
Sinking Current
vs.
Output Voltage
Source Current
vs.
Output Voltage
Open Loop Frequency Response
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APPLICATION HINTS
The LM321 op amp can operate with a single or dual power supply voltage, has true-differential inputs, and
remain in the linear mode with an input common-mode voltage of 0 VDC. This amplifier operates over a wide
range of power supply voltages, with little change in performance characteristics. At 25°C amplifier operation is
possible down to a minimum supply voltage of 3V.
Large differential input voltages can be easily accommodated and, as input differential voltage protection diodes
are not needed, no large input currents result from large differential input voltages. The differential input voltage
may be larger than V+ without damaging the device. Protection should be provided to prevent the input voltages
from going negative more than −0.3 VDC (at 25°C).An input clamp diode with a resistor to the IC input terminal
can be used.
To reduce the power supply drain, the amplifier has a class A output stage for small signal levels which converts
to class B in a large signal mode. This allows the amplifiers to both source and sink large output currents.
Therefore both NPN and PNP external current boost transistors can be used to extend the power capability of
the basic amplifiers. The output voltage needs to raise approximately 1 diode drop above ground to bias the onchip vertical PNP transistor for output current sinking applications.
For AC applications, where the load is capacitively coupled to the output of the amplifier, a resistor should be
used, from the output of the amplifier to ground to increase the class A bias current and to reduce distortion.
Capacitive loads which are applied directly to the output of the amplifier reduce the loop stability margin. Values
of 50pF can be accommodated using the worst-case non-inverting unity gain connection. Large closed loop
gains or resistive isolation should be used if large load capacitance must be driven by the amplifier.
The bias network of the LM321 establishes a supply current which is independent of the magnitude of the power
supply voltage over the range of from 3 VDC to 30 VDC.
Output short circuits either to ground or to the positive power supply should be of short time duration. Units can
be destroyed, not as a result of the short circuit current causing metal fusing, but rather due to the large increase
in IC chip dissipation which will cause eventual failure due to excessive junction temperatures. The larger value
of output source current which is available at 25°C provides a larger output current capability at elevated
temperatures than a standard IC op amp.
The circuits presented in the section on typical applications emphasize operation on only a single power supply
voltage. If complementary power supplies are available, all of the standard op amp circuits can be used. In
general, introducing a pseudo-ground (a bias voltage reference of V+/2) will allow operation above and below this
value in single power supply systems. Many application circuits are shown which take advantage of the wide
input common-mode voltage range which includes ground. In most cases, input biasing is not required and input
voltages which range to ground can easily be accommodated.
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LM321
TYPICAL APPLICATIONS
Non-Inverting DC Gain (0V Input = 0V Output)
DC Summing Amplifier (V)
(IN's ≥ 0 VDC and VO ≥ VDC)
Amplitude Modulator Circuit
Where: V0 = V1 + V2 - V3 - V4, (V1+V2) ≥ (V3 + V4) to keep VO > 0
VDC
Power Amplifier
LED Driver
V0 = 0 VDC for VIN = 0 VDC, AV = 10
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Fixed Current Sources
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Lamp Driver
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