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
Current-feedback amplifiers eliminate this difficulty Because their -input is a very low impedance
capacitance at the summing point of an inverting operational circuit is far less troublesome Here is a
table of results of various current-feedback circuits used in the inverting circuit
Operational
Power
b3 dB
0 1 dB
Amplifier
Supplies
Rf
RIN
Rg
Bandwidth
Bandwidth
Peaking
EL2020
EL2020
EL2130
EL2030
g5V
g15V
g5V
g15V
1k
910
1k
910
1k
910
1k
910
29 MHz
4 3 MHz
0
34 MHz
5 3 MHz
0
61 MHz
9 7 MHz
0
82 MHz
12 3 MHz
0
EL2171
g5V
2k
1 8k
1k
114 MHz
11 MHz
with the EL2171 the EL2082 had g15V supplies and the EL2171 required a 150X output load
1 2 dB
The EL2120 and EL2090 are suitable in this circuit but they are compensated for 300X feedback
resistors RIN would have to be reduced greatly to obtain unity gain and the increased signal currents
would cause the EL2082 to display much increased distortion They could be used if the input resistor
were maintained at 910X and Rf reduced for a b gain or if Rf e 1k and an overall bandwidth of
25 MHz were acceptable
The EL2082 can also be used within an op-amp’s feedback loop
J 1V
Gain e b
RF a 95X
VGAIN
RIN
EL2082 in feedback
inverting gain
2082 – 15
With voltage-mode op-amps the same concern about capacitance at the summing node exists so Cf and
CIN should be used As before current-feedback amplifiers tend to solve the problem However in this
circuit the inherent phase lag of the EL2082 detracts from the phase margin of the op-amp and some
overall bandwidth reduction may result The EL2082 appears as a 3 0 ns delay well past 100 MHz
Thus for a 20 MHz loop bandwidth the EL2082 will subtract 20 MHz c 3 0 ns c 360 degrees e 21 6
degrees The loop path should have at least 55 degrees of phase margin for low ringing in this connec-
tion Loop bandwidth is always reduced by the ratio RIN (RIN a Rf) with voltage mode op-amps
9
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