参数资料
| 型号： | AD8307AR-REEL |
| 厂商： | Analog Devices Inc |
| 文件页数： | 13/24页 |
| 文件大小： | 0K |
| 描述： | IC LOGARITHMIC AMP 8-SOIC T/R |
| 标准包装： | 2,500 |
| 类型： | 对数放大器 |
| 应用： | 接收器信号强度指示（RSSI） |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 8-SOIC（0.154"，3.90mm 宽） |
| 供应商设备封装： | 8-SO |
| 包装： | 带卷 (TR) |
AD8307
Rev. D | Page 20 of 24
APPLICATIONS INFORMATION
The AD8307 is a highly versatile and easily applied log amp
requiring very few external components. Most applications of this
device can be accommodated using the simple connections shown
in the preceding section.
BUFFERED OUTPUT
The output can be buffered and the slope optionally increased by
using an op amp. If the single-supply capability is to be preserved,
a suitable component is the AD8031. Like the AD8307, it is
capable of operating from a 2.7 V supply and features a rail-to-
rail output capability; it is available in a 5-lead version and in
can be increased to 50 mV/dB (1 V per decade), requiring a 5 V
supply (90 dB times 50 mV is a 4.5 V swing). VR1 provides a
±10% slope adjustment; VR2 provides a ±3 dB intercept range.
With R2 = 4.99 kΩ, the slope is adjustable to 25 mV/dB, allowing
the use of a 2.7 V supply. Setting R2 to 80.6 kΩ, it is raised to
100 mV/dB, providing direct reading in decibels on a digital
voltmeter. Because a 90 dB range now corresponds to a 9 V swing,
a supply of at least this amount is needed for the op amp.
20mV/dB
AD8031
01
08
2-
0
38
OUTPUT
50mV/dB
±10%
AD8307
INPUT
–75dBm TO
+16dBm
INP VPS ENB INT
INM COM OFS OUT
NC
NC = NO CONNECT
87
6
5
23
4
1
4.7
VR2
50k
R2
30.1k
COM
R1
20k
RS
0.1F
VP, 2.7V TO 5.5V
±3dB
VR1
50k
32.4k
C1
FOR VP = 3V, RS = 20k
VP = 5V, RS = 51k
Figure 38. Log Amp with Buffered Output
C1 is optional; it lowers the corner frequency of the low-pass
output filter. A value of 0.1 μF should be used for applications in
which the output is measured on a voltmeter or other low speed
device. On the other hand, when C1 is omitted, the 10% to 90%
response time is under 200 ns and is typically 300 ns to 99% of
the final value. To achieve faster response times, it is necessary
to lower the load resistance at the output of the AD8307, then
restore the scale using a higher gain in the op amp. Using 8.33 kΩ,
the basic slope is 10 mV/dB; this can be restored to 25 mV/dB
using a buffer gain of 2.5. The overall 10% to 90% response time
is under 100 ns. Figure 39 shows how the output current capability
can be augmented to drive a 50 Ω load; RT optionally provides
reverse termination, which halves the slope to 12.5 mV/dB.
FOUR-POLE FILTER
In low frequency applications, for example, audio down to
20 Hz, it is useful to employ the buffer amplifier as a multipole
low-pass filter to achieve low output ripple while maintaining a
rapid response time to changes in signal level.
25mV/dB
2N3904
10mV/dB
±18%
AD8031
01
08
2-
0
39
OUTPUT
50
MINIMUM
AD8307
INPUT
–75dBm TO
+16dBm
INP VPS ENB INT
INM COM OFS OUT
NC
NC = NO CONNECT
87
6
5
23
4
1
4.7
VR2
50k
R2
3.01k
R1
2k
RS
0.1F
VP, 2.7V TO 5.5V
±3dB
VR1
5k
6.34k
RT
(OPTIONAL)
COM
Figure 39. Cable Driving Log Amp
In Figure 40, the capacitor values are chosen for operation in the
audio field, providing a corner frequency of 10 Hz, an attenuation
of 80 dB/decade above this frequency, and a 1% settling time of
150 ms (0.1% in 175 ms). The residual ripple is 4 mV (±0.02 dB)
when the input to the AD8307 is at 20 Hz. This filter can easily
be adapted to other frequencies by proportional scaling of C5 to C7
(for example, for 100 kHz use 100 pF). Placed ahead of a digital
multimeter, the convenient slope scaling of 100 mV/dB requires
only a repositioning of the decimal point to read directly in
decibels. The supply voltage for the filter must be large enough to
support the dynamic range; a minimum of 9 V is needed for most
applications; 12 V is recommended.
VR2
50k
SLOPE
01
08
2-
04
0
OUTPUT
100mV/dB
AD8307
INPUT 5mV
TO 160V rms
INP VPS ENB INT
INM COM OFS OUT
87
6
5
23
4
1
4.7
VR1
2k
NC
R1
50k
93k
80.6k
32.4k
34k
422
0.1F
VP
C6
1F
75k
C7
1F
C2
10F
C3
2.5nF
+
C1
10F
OP AMP IS AD8032 SCALE
C1 TO C8 AS NEEDED.
NOTE POLARITIES IF TANTALUM
CAPACITORS ARE USED.
C4 1
F
+
C8
1F
7.32k
100k
34k
+
C5
1F
INT ±4dB
COM
Figure 40. Log Amp with Four-Pole Low-Pass Filter
Figure 40 also shows the use of an input attenuator that can
optionally be employed to produce a useful wide range ac
voltmeter with direct decibel scaling. The basic range of 73
dBm to +17 dBm (that is, 50 μV rms to 1.6 V rms, for sine
excitations) is shifted for illustrative purposes to 5 mV to 160 V
rms (at which point the power in R1 is 512 mW). Because the
basic input resistance of the AD8307 is not precise, VR1 is used
to center the signal range at its input, doubling as a ±4 dB intercept
adjustment. The low frequency response extends to 15 Hz; a
higher corner frequency can be selected as needed by scaling C1
and C2. The shunt capacitor, C3, is used to lower the high
frequency bandwidth
to about 100 kHz, and thus lower the susceptibility to spurious
signals. Other values should be chosen as needed for the coupling
and filter capacitors.
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| AD8307AR-REEL7 | 功能描述:IC LOGARITHMIC AMP 8-SOIC RoHS:否 类别:集成电路 (IC) >> 线性 - 放大器 - 专用 系列:- 产品培训模块:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 标准包装:60 系列:- 类型:可变增益放大器 应用:CATV 安装类型:表面贴装 封装/外壳:20-WQFN 裸露焊盘 供应商设备封装:20-TQFN-EP（5x5） 包装:托盘 |
| AD8307ARZ | 功能描述:IC LOGARITHMIC AMP 92DB 8-SOIC RoHS:是 类别:集成电路 (IC) >> 线性 - 放大器 - 专用 系列:- 产品培训模块:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 标准包装:60 系列:- 类型:可变增益放大器 应用:CATV 安装类型:表面贴装 封装/外壳:20-WQFN 裸露焊盘 供应商设备封装:20-TQFN-EP（5x5） 包装:托盘 |
| AD8307ARZ | 制造商:Analog Devices 功能描述:Logarithmic Amplifier IC |
| AD8307ARZ-REEL | 功能描述:IC AMP LOGARITHMIC 8SOIC RoHS:是 类别:集成电路 (IC) >> 线性 - 放大器 - 专用 系列:- 产品培训模块:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 标准包装:60 系列:- 类型:可变增益放大器 应用:CATV 安装类型:表面贴装 封装/外壳:20-WQFN 裸露焊盘 供应商设备封装:20-TQFN-EP（5x5） 包装:托盘 |
| AD8307ARZ-RL7 | 功能描述:IC AMP LOGARITHMIC 8-SOIC RoHS:是 类别:集成电路 (IC) >> 线性 - 放大器 - 专用 系列:- 产品培训模块:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 标准包装:60 系列:- 类型:可变增益放大器 应用:CATV 安装类型:表面贴装 封装/外壳:20-WQFN 裸露焊盘 供应商设备封装:20-TQFN-EP（5x5） 包装:托盘 |
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