- 您現(xiàn)在的位置：買賣IC網(wǎng) > PDF目錄358885 > LMV712BLX (NATIONAL SEMICONDUCTOR CORP) Low Power, Low Noise, High Output, RRIO Dual Operational Amplifier with Independent Shutdown PDF資料下載
參數(shù)資料
| 型號： | LMV712BLX |
| 廠商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分類： | 運算放大器 |
| 英文描述： | Low Power, Low Noise, High Output, RRIO Dual Operational Amplifier with Independent Shutdown |
| 中文描述： | DUAL OP-AMP, 3200 uV OFFSET-MAX, 5 MHz BAND WIDTH, PBGA10 |
| 封裝： | MICRO, MO-211BD, SMD-10 |
| 文件頁數(shù)： | 10/14頁 |
| 文件大?。?/td> | 505K |
| 代理商： | LMV712BLX |
Application Information
Theory of Operation
The LMV712 dual op amp is derived from the LMV711 single
op amp. Figure 1 contains a simplified schematic of one
channel of the LMV712.
Rail-to-Rail input is achieved by using in parallel, one NMOS
differential pair (MN1 and MN2) and one PMOS differential
pair (MP1 and MP2). When the common mode input voltage
(V
CM
) is near V
+
, the NMOS pair is on and the PMOS pair is
off. When V
CM
is near V
, the NMOS pair is off and the
PMOS pair is on. When V
CM
is between V
+
and V
, internal
logic decides how much current each differential pair will get.
This special logic ensures stable and low distortion amplifier
operation within the entire common mode voltage range.
Because both input stages have their own offset voltage
(V
) characteristic, the offset voltage of the LMV712 be-
comes a function of V
. V
OS
has a crossover point at 1.4V
above V
. Refer to the ’V
vs. V
’ curve in the Typical
Performance Characteristics section. Caution should be
taken in situations where input signal amplitude is compa-
rable to V
value and/or the design requires high accuracy.
In these situations, it is necessary for the input signal to
avoid the crossover point.
The current coming out of the input differential pairs gets
mirrored through two folded cascode stages (Q1, Q2, Q3,
Q4) into the ’class AB control’ block. This circuitry generates
voltage gain, defines the op amp’s dominant pole and limits
the maximum current flowing at the output stage. MN3 intro-
duces a voltage level shift and acts as a high impedance to
low impedance buffer.
The output stage is composed of a PMOS and a NPN
transistor in a common source/emitter configuration, deliver-
ing a rail-to-rail output excursion.
The MN4 transistor ensures that the LMV712 output remains
near V
when the amplifier is in shutdown mode.
Shutdown Pin
The LMV712 offers independent shutdown pins for the dual
amplifiers. When the shutdown pin is tied low, the respective
amplifier shuts down and the supply current is reduced to
less than 1μA. In shutdown mode, the amplifier’s output level
stays at V
. In a 2.7V operation, when a voltage between
1.5V to 2.7V is applied to the shutdown pin, the amplifier is
enabled. As the amplifier is coming out of the shutdown
mode, the output waveform ramps up without any glitch. This
is demonstrated in Figure 2
A glitch-free output waveform is highly desirable in many
applications, one of which is power amplifier control loops. In
this application, the LMV712 is used to drive the power
amplifier’s power control. If the LMV712 did not have a
smooth output ramp during turn on, it would directly cause
the power amplifier to produce a glitch at its output. This
adversely affects the performance of the system.
To enable the amplifier, the shutdown pin must be pulled
high. It should not be left floating in the event that any
leakage current may inadvertently turn off the amplifier.
Printed Circuit Board Consideration
To properly bypass the power supply, several locations on a
printed circuit board need to be considered. A 6.8μF or
greater tantalum capacitor should be placed at the point
where the power supply for the amplifier is introduced onto
the board. Another 0.1μF ceramic capacitor should be
placed as close as possible to the power supply pin of the
amplifier. If the amplifier is operated in a single power supply,
only the V
+
pin needs to be bypassed with a 0.1μF capacitor.
If the amplifier is operated in a dual power supply, both V
+
and V
pins need to be bypassed.
It is good practice to use a ground plane on a printed circuit
board to provide all components with a low inductive ground
connection.
Surface mount components in 0805 size or smaller are
recommended in the LMV712 application circuits. Designers
can take advantage of the micro SMD, MSOP and LLP
miniature sizes to condense board layout in order to save
space and reduce stray capacitance.
Capacitive Load Tolerance
The LMV712 can directly drive 200pF in unity-gain without
oscillation. The unity-gain follower is the most sensitive con-
figuration to capacitive loading. Direct capacitive loading
reduces the phase margin of amplifiers. The combination of
the amplifier’s output impedance and the capacitive load
induces phase lag. This results in either an under-damped
pulse response or oscillation. To drive a heavier capacitive
load, Figure 3 can be used.
10137031
FIGURE 1.
10137030
FIGURE 2.
L
www.national.com
10
相關PDF資料 |
PDF描述 |
|---|---|
| LMV712LD | Low Power, Low Noise, High Output, RRIO Dual Operational Amplifier with Independent Shutdown |
| LMV712LDX | Low Power, Low Noise, High Output, RRIO Dual Operational Amplifier with Independent Shutdown |
| LMV712MM | Low Power, Low Noise, High Output, RRIO Dual Operational Amplifier with Independent Shutdown |
| LMV712MMX | Low Power, Low Noise, High Output, RRIO Dual Operational Amplifier with Independent Shutdown |
| LMV721 | 10MHz, Low Noise, Low Voltage, and Low Power Operational Amplifier |
相關代理商/技術參數(shù) |
參數(shù)描述 |
|---|---|
| LMV712BLX/NOPB | 制造商:Texas Instruments 功能描述:OP Amp Dual GP R-R I/O 5.5V 10-Pin uSMD T/R |
| LMV712IDGSR | 功能描述:運算放大器 - 運放 Low-Pwr Low-Noise Hi-Out RRIO Dual RoHS:否 制造商:STMicroelectronics 通道數(shù)量:4 共模抑制比（最小值）:63 dB 輸入補償電壓:1 mV 輸入偏流（最大值）:10 pA 工作電源電壓:2.7 V to 5.5 V 安裝風格:SMD/SMT 封裝 / 箱體:QFN-16 轉(zhuǎn)換速度:0.89 V/us 關閉:No 輸出電流:55 mA 最大工作溫度:+ 125 C 封裝:Reel |
| LMV712IDGSR | 制造商:Texas Instruments 功能描述:IC OP-AMP GP R-R 5MHZ DUAL 10MSOP |
| LMV712IDGSRG4 | 功能描述:運算放大器 - 運放 Low-Pwr Low-Noise Hi-Out RRIO Dual RoHS:否 制造商:STMicroelectronics 通道數(shù)量:4 共模抑制比（最小值）:63 dB 輸入補償電壓:1 mV 輸入偏流（最大值）:10 pA 工作電源電壓:2.7 V to 5.5 V 安裝風格:SMD/SMT 封裝 / 箱體:QFN-16 轉(zhuǎn)換速度:0.89 V/us 關閉:No 輸出電流:55 mA 最大工作溫度:+ 125 C 封裝:Reel |
| LMV712IDGST | 功能描述:運算放大器 - 運放 Low-Pwr Low-Noise Hi-Out RRIO Dual RoHS:否 制造商:STMicroelectronics 通道數(shù)量:4 共模抑制比（最小值）:63 dB 輸入補償電壓:1 mV 輸入偏流（最大值）:10 pA 工作電源電壓:2.7 V to 5.5 V 安裝風格:SMD/SMT 封裝 / 箱體:QFN-16 轉(zhuǎn)換速度:0.89 V/us 關閉:No 輸出電流:55 mA 最大工作溫度:+ 125 C 封裝:Reel |
發(fā)布緊急采購，3分鐘左右您將得到回復。