参数资料
| 型号： | AD640JPZ |
| 厂商： | Analog Devices Inc |
| 文件页数： | 6/16页 |
| 文件大小： | 0K |
| 描述： | IC AMP LOG 2.3MA 20PLCC |
| 标准包装： | 1 |
| 放大器类型： | 对数 |
| 电路数： | 1 |
| -3db带宽： | 350MHz |
| 电流 - 输入偏压： | 7µA |
| 电压 - 输入偏移： | 50µV |
| 电流 - 电源： | 35mA |
| 电流 - 输出 / 通道： | 2.3mA |
| 电压 - 电源，单路/双路(±)： | ±4.5 V ~ 7.5 V |
| 工作温度： | 0°C ~ 70°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 20-LCC（J 形引线） |
| 供应商设备封装： | 20-PLCC（9x9） |
| 包装： | 管件 |
AD640
REV. C
–14–
15
13
14
16
19
18
17
11
12
20
6
8
7
5
3
4
10
9
1
2
SIG
+IN
ATN
OUT
CKT
COM
RG1 RG0 RG2 LOG
OUT
LOG
COM
+VS
SIG
+OUT
SIG
–IN
ATN
LO
ATN
COM
BL1
BL2
ITC
–VS
SIG
–OUT
1k
ATN
COM
ATN
IN
U1 AD640
NC
R1
R2
NC
15
13
14
16
19
18
17
11
12
20
6
8
7
5
3
4
10
9
1
2
SIG
+IN
ATN
OUT
CKT
COM
RG1 RG0 RG2 LOG
OUT
LOG
COM
+VS
SIG
+OUT
SIG
–IN
ATN
LO
ATN
COM
BL1
BL2
ITC
–VS
SIG
–OUT
1k
ATN
COM
ATN
IN
U2 AD640
C1
47pF
R3
100
68
C2
47pF
R4
100
18
L1
(SEE
TEXT)
18
–6V
+6V
68
–6V
4.7
U3
AD844
LOG
OUTPUT
+50mV/dB
(LO)
+6V
4.7
DENOTES A CONNECTION TO THE GROUND PLANE;
OBSERVE COMMON CONNECTIONS WHERE SHOWN.
ALL UNMARKED CAPACITORS ARE 0.1 F CERAMIC.
SEE TEXT FOR VALUES OF NUMBERED COMPONENTS.
SIGNAL
INPUT
R13
1.13k
(SEE TEXT)
NC = NO CONNECT
Figure 30. Complete 70 dB Dynamic Range Converter for 50 MHz–150 MHz Operation
must be some resistance at Pins 1 and 20 across which the offset
compensation voltage is developed. The values shown in the
figure assume that we wish to terminate a 50
source at Pin 20.
The 50
resistor at Pin 1 is essential, both to minimize offsets
due to bias current mismatch and because the outputs at Pins
10 and 11 can only swing negatively (from ground to –180 mV)
whereas we need to cater for input offsets of either polarity.
For a sine input of 1
V amplitude (–120 dBV) and in the
absence of offset, the differential voltage at Pins 10 and 11 of
U2 would be almost sinusoidal but 100,000 times larger, or
100 mV. The last limiter in U2 would be entering saturation. A
1
V input offset added to this signal would put the last limiter
well into saturation, and its output would then have a different
average value, which is extracted by the low-pass network and
delivered back to the input. For larger signals, the output ap-
proaches a square wave for zero input offset and becomes rect-
angular when offset is present. The duty cycle modulation of
this output now produces the nonzero average value. Assume a
maximum required differential output of 100 mV (after averag-
ing in C1 and C2) as shown in Figure 29. R3 through R6 can
now be chosen to provide
±500 V of correction range, and with
these values the input offset is reduced by a factor of 500. Using
4.7
F capacitors, the time constant of the network is about
1.2 ms, and its corner frequency is at 13.5 Hz. The closed loop
high-pass corner (for small signals) is, therefore, at 1.35 MHz.
Bandwidth/Dynamic Range Trade-Offs
The first stage noise of the AD640 is 2 nV/
√Hz (short circuited
input) and the full bandwidth of the cascaded ten stages is about
150 MHz. Thus, the noise referred to the input is 24.5
V rms,
or –79 dBm, which would limit the dynamic range to 77 dBs
(–79 dBm to –2 dBm). In practice, the source resistances will
also generate noise, and the full bandwidth dynamic range will
be less than this.
A low-pass filter between U1 and U2 can limit the noise band-
width and extend the dynamic range. The simplest way to do
this is by the addition of a pair of grounded capacitors at the
signal outputs of U1 (shown as C1 and C2 in Figure 32). The
20
1
11
10
U2
U1
AVE = –140mV
INPUT
R1
50
R2
50
AVE = –40mV
R3
4.99k
R5
4.99k
–200 V
–700 V
4 A
14 A
20
1
11
10
C1
C2
R4
4.99k
R6
4.99k
Figure 29. Feedback Offset Correction Network
–3 dB frequency of the filter must be above the highest fre
quency to be handled by the converter; if not, nonlinearity in
the transfer function will occur. This can be seen intuitively by
noting that the system would then contract to a single AD640 at
very high frequencies (when U2 has very little input). At inter-
mediate frequencies, U2 will contribute less to the output than
would be the case if there were no interstage attenuation, result-
ing in a kink in the transfer function.
More complex filtering may be considered. For example, if the
signal has a fairly narrow bandwidth, the simple chokes shown
in Figure 28 might be replaced by one or more parallel tuned
circuits. Two separate tuned circuits or transformer coupling
should be used to eliminate all undesirable hf common mode
coupling between U1 and U2. The choice of Q for these circuits
requires compromise. Frequency sensitive nonlinearities can
arise at the edges of the band if the Q is set too high; if too low,
the transmission of the signal from U1 to U2 will be affected
even at the center frequency, again resulting in nonlinearity in
the conversion response. In calculating the Q, note that the
resistance from Pins 10 and 11 to ground is 75
. The input
resistance at Pins 1 and 20 is very high, but the capacitances at
these pins must also be factored into the total LCR circuit.
PRACTICAL APPLICATIONS
We show here two applications, using cascaded AD640s to
achieve a wide dynamic range. As already mentioned, the use of
a differential signal path and differential logarithmic outputs
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| AD640JPZ-REEL7 | 功能描述:IC AMP LOG 2.3MA 20PLCC RoHS:是 类别:集成电路 (IC) >> Linear - Amplifiers - Instrumentation 系列:- 标准包装:50 系列:- 放大器类型:J-FET 电路数:2 输出类型:- 转换速率:3.5 V/µs 增益带宽积:1MHz -3db带宽:- 电流 - 输入偏压:30pA 电压 - 输入偏移:2000µV 电流 - 电源:200µA 电流 - 输出 / 通道:- 电压 - 电源，单路/双路(±):7 V ~ 36 V，±3.5 V ~ 18 V 工作温度:0°C ~ 70°C 安装类型:通孔 封装/外壳:8-DIP（0.300"，7.62mm） 供应商设备封装:8-PDIP 包装:管件 |
| AD640T | 制造商:AD 制造商全称:Analog Devices 功能描述:DC-Coupled Demodulating 120 MHz Logarithmic Amplifier |
| AD640TCHIPS | 制造商:AD 制造商全称:Analog Devices 功能描述:DC-Coupled Demodulating 120 MHz Logarithmic Amplifier |
| AD640TD | 制造商:AD 制造商全称:Analog Devices 功能描述:DC-Coupled Demodulating 120 MHz Logarithmic Amplifier |
| AD640TD/883B | 功能描述:对数放大器 I.C. LOG AMP IC RoHS:否 制造商:Texas Instruments 通道数量:3 带宽:3 dB 共模抑制比（最小值）: 输入补偿电压:+/- 7 mV 输入电压范围（最大值）:5.5 V 工作电源电压:4.5 V to 5.5 V 电源电流:+/- 15 mA 工作温度范围:- 40 C to +85 C 安装风格:SMD/SMT 封装 / 箱体:VQFN-16 封装:Reel |
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