AD603 Просмотр технического описания (PDF) - Analog Devices
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AD603 Datasheet PDF : 25 Pages
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AD603
VC1
1 GPOS VPOS 8
VPOS
AD603
VC2
2 GNEG VOUT 7
VOUT
VIN
3 VINP VNEG 6
VNEG
2.15kΩ
4 COMM FDBK 5
5.6pF
Figure 33. 0 dB to 40 dB; 30 MHz Bandwidth
VC1
1 GPOS VPOS 8
VPOS
AD603
VC2
2 GNEG VOUT 7
VOUT
VIN
3 VINP VNEG 6
VNEG
4 COMM FDBK 5
18pF
Figure 34. 10 dB to 50 dB; 9 MHz to Set Gain
52
50
–1:VdB (OUT)
48
46
44
VdB (OUT)
42
–2:VdB (OUT)
40
38
36
34
32
30
10
100
1k
10k
100k
1M
REXT (Ω)
Figure 35. Gain vs. REXT, Showing Worst-Case Limits Assuming Internal
Resistors Have a Maximum Tolerance of 20%
Data Sheet
Optionally, when a resistor is placed from FDBK to COMM,
higher gains can be achieved. This fourth mode is of limited
value because of the low bandwidth and the elevated output
offsets; it is thus not included in Figure 32, Figure 33, or
Figure 34.
The gain of this amplifier in the first two modes is set by the
ratio of on-chip laser-trimmed resistors. While the ratio of these
resistors is very accurate, the absolute value of these resistors
can vary by as much as ±20%. Therefore, when an external
resistor is connected in parallel with the nominal 6.44 kΩ ± 20%
internal resistor, the overall gain accuracy is somewhat poorer.
The worst-case error occurs at about 2 kΩ (see Figure 36).
1.2
–1:VdB (OUT) – (–1):VdB (OREF)
1.0
0.8
0.6
0.4
0.2
0
–0.2
–0.4
–0.6
–0.8
VdB (OUT) – VdB (OREF)
–1.0
10
100
1k
10k
100k
1M
REXT (Ω)
Figure 36. Worst-Case Gain Error, Assuming Internal Resistors Have a
Maximum Tolerance of −20% (Top Curve) or = 20% (Bottom Curve)
While the gain bandwidth product of the fixed-gain amplifier is
about 4 GHz, the actual bandwidth is not exactly related to the
maximum gain. This is because there is a slight enhancing of
the ac response magnitude on the maximum bandwidth range,
due to higher order poles in the open-loop gain function; this
mild peaking is not present on the higher gain ranges. Figure 32,
Figure 33, and Figure 34 show how an optional capacitor may
be added to extend the frequency response in high gain modes.
Rev. K | Page 14 of 24
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