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參數(shù)資料
| 型號(hào)： | LMH6502MA |
| 廠商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分類： | 模擬信號(hào)調(diào)理 |
| 英文描述： | Wideband, Low Power, Linear-in-dB Variable Gain Amplifier |
| 中文描述： | SPECIALTY ANALOG CIRCUIT, PDSO14 |
| 封裝： | SOIC-14 |
| 文件頁數(shù)： | 16/19頁 |
| 文件大?。?/td> | 941K |
| 代理商： | LMH6502MA |
Application Information
(Continued)
National Semiconductor suggests the following evaluation
boards as a guide for high frequency layout and as an aid in
device testing and characterization:
Device
Package
Evaluation Board
Part Number
CLC730033
CLC730146
LMH6502MA
LMH6502MT
SOIC-14
TSSOP-14
The evaluation board is shipped when a device sample
request is placed with National Semiconductor
SINGLE SUPPLY OPERATION
It is possible to operate the LMH6502 with a single supply. To
do so, tie pin 11 (GND) to a potential about mid point
between V
+
and V
. Two examples are shown in
Figure 4
&
Figure 5
.
OPERATING AT LOWER SUPPLY VOLTAGES
The LMH6502 is rated for operation down to 5V supplies (V
+
-V
). There are some specifications shown for operation at
±
2.5V within the data sheet (i.e. Frequency Response,
CMRR, PSRR, Gain vs. V
G
, etc.). Compared to
±
5V opera-
tion, at lower supplies:
a) V
G
range shifts lower.
Here are the approximate expressions for various V
G
voltages as a function of V
+
:
TABLE 1. V
G
Definition Based on V
+
V
G
V
G_MIN
V
G_MID
V
G_MAX
Definition
Gain Cut-off
A
VMAX
/2
A
VMAX
Expression (V)
0.2 x V
+
1
0.2 x V
+
0.2 x V
+
+1
b) V
(maximum permissible voltage on V
) is re-
duced. This is due to limitations within the device arising
from transistor headroom. Beyond this limit, device per-
formance will be affected (non-destructive). This could
reveal itself as premature high frequency response roll-
off. With
±
2.5V supplies, V
G_LIMIT
is below 1.1V whereas
V
G
= 1.5V is needed to get maximum gain. This means
that operating under these conditions has reduced the
maximum permissible voltage on V
G
to a level below
what is needed to get Max gain. If supply voltages are
asymmetrical with V
+
being lower, further "pinching" of
V
range could result; for example, with V
+
= 2V, and V
= 3V, V
= 0.40V which results in maximum gain
being 2.5dB less than what would be expected when V
S
is higher.
c) "Max_gain" reduces. There is an intrinsic reduction in
max gain when the total supply voltage is reduced (see
Typical Performance Characteristics plots for Gain vs. V
G
(V
=
±
2.5V). In addition, there is the more drastic
mechanism described in "b" above. Beyond V
G_LIMIT
,
high frequency response is also effected.
Application Circuits
AGC LOOP
Figure 6
shows a typical AGC circuit. The LMH6502 is
followed up with a LMH6714 for higher overall gain. The
output of the LMH6714 is rectified and fed to an inverting
integrator using a LMH6657 (wideband voltage feedback op
amp). When the output voltage, V
, is too large the inte-
grator output voltage ramps down reducing the net gain of
the LMH6502 and V
. If the output voltage is too small,
the integrator ramps up increasing the net gain and the
output voltage. Actual output level is set with R
. To prevent
shifts in DC output voltage with DC changes in input signal
level, trim pot R
is provided. AGC circuits are always limited
in the range of input signals over which constant output level
can be maintained. In this circuit, we would expect that
reasonable AGC action could be maintained for at least
40dB. In practice, rectifier dynamic range limits reduce this
slightly.
20067746
FIGURE 4. AC Coupled Single Supply VGA
20067747
FIGURE 5. Transformer Coupled Single Supply VGA
L
www.national.com
16
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LMH6502MA/NOPB | 功能描述:特殊用途放大器 Wdbd, Lo Pwr, Linear -in-dB Var Gain Amp RoHS:否 制造商:Texas Instruments 通道數(shù)量:Single 共模抑制比（最小值）: 輸入補(bǔ)償電壓: 工作電源電壓:3 V to 5.5 V 電源電流:5 mA 最大功率耗散: 最大工作溫度:+ 70 C 最小工作溫度:- 40 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:QFN-20 封裝:Reel |
| LMH6502MAX | 功能描述:特殊用途放大器 RoHS:否 制造商:Texas Instruments 通道數(shù)量:Single 共模抑制比（最小值）: 輸入補(bǔ)償電壓: 工作電源電壓:3 V to 5.5 V 電源電流:5 mA 最大功率耗散: 最大工作溫度:+ 70 C 最小工作溫度:- 40 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:QFN-20 封裝:Reel |
| LMH6502MAX/NOPB | 功能描述:特殊用途放大器 RoHS:否 制造商:Texas Instruments 通道數(shù)量:Single 共模抑制比（最小值）: 輸入補(bǔ)償電壓: 工作電源電壓:3 V to 5.5 V 電源電流:5 mA 最大功率耗散: 最大工作溫度:+ 70 C 最小工作溫度:- 40 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:QFN-20 封裝:Reel |
| LMH6502MT | 功能描述:特殊用途放大器 RoHS:否 制造商:Texas Instruments 通道數(shù)量:Single 共模抑制比（最小值）: 輸入補(bǔ)償電壓: 工作電源電壓:3 V to 5.5 V 電源電流:5 mA 最大功率耗散: 最大工作溫度:+ 70 C 最小工作溫度:- 40 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:QFN-20 封裝:Reel |
| LMH6502MT/NOPB | 功能描述:特殊用途放大器 RoHS:否 制造商:Texas Instruments 通道數(shù)量:Single 共模抑制比（最小值）: 輸入補(bǔ)償電壓: 工作電源電壓:3 V to 5.5 V 電源電流:5 mA 最大功率耗散: 最大工作溫度:+ 70 C 最小工作溫度:- 40 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:QFN-20 封裝:Reel |
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