EL2082C データシートの表示（PDF） - Elantec -> Intersil
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EL2082C Datasheet PDF : 16 Pages
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EL2082C
Current-Mode Multiplier
Applications Information Contd
The output current could be terminated with a 1 kX load resistor to achieve a nominal voltage gain of 1
at the EL2082 but the IOUT load and stray capacitances would limit bandwidth greatly The lowest
practical total capacitance at IOUT is about 12 pF and this gives a 13 MHz bandwidth with a 1 kX
load In the above example a 100X load is used for an upper limit of 130 MHz The operational
amplifier gives a gain of a10 to bring the overall gain to unity Wider bandwidth yet can be had by
installing CIN This is a very small capacitor typically 1 pf – 2 pF and it bolsters the gain above
100 MHz Here is a table of results for this circuit used with various amplifiers
Operational
Power
b3 dB
0 1 dB
Amplifier
Supplies
Rf
Rg
CIN
Bandwidth
Bandwidth
Peaking
EL2020
EL2020
EL2130
EL2030
EL2090
EL2120
EL2120
EL2070
EL2071
EL2075
g5V
g15V
g5V
g15V
g15V
g5V
g15V
g5V
g5V
g5V
620
68
620
68
620
68
620
68
240
27
220
24
220
24
200
22
2 pF
1 5K
240
2 pF
620
68
2 pF
34 MHz
40 MHz
73 MHz
93 MHz
60 MHz
57 MHz
65 MHz
150 MHz
200 MHz
270 MHz
5 6 MHz
7 4 MHz
11 MHz
12 MHz
10 MHz
10 MHz
11 MHz
30 MHz
30 MHz
30 MHz
0
0
1 0 dB
1 3 dB
0 5 dB
0 4 dB
0 3 dB
0 4 dB
0
1 5 dB
Maximum bandwidth is maintained over a gain range of a6 to b16 dB bandwidth drops at lower
gains If wider gain range with full bandwidth is required two or more EL2082’s can be cascaded with
the IOUT of one directly driving the IIN of the next
x The EL2082 can also be used with an I V operational circuit
J Gain e bVGAIN
RF
1V RIN a95X
Inverting
EL2082 a Op-Amp
2082 – 14
The circuit above gives a negative gain The main concern of this connection involves the total IOUT
and stray capacitances at the amplifier’s input When using traditional op-amps the pole caused by
these capacitances can make the amplifier less stable and even cause oscillations in amplifiers whose
gain-bandwidth is greater than 5 MHz A typical cure is to add a capacitor Cf in the 2 pF–10 pF range
This will reduce overall bandwidth so a capacitor CIN can be added to regain frequency response The
ratio Cf CIN is made equal to RIN Rf
8
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