el2082 Intersil Corporation, el2082 Datasheet - Page 8

• Manufacturer Part Number: el2082
• Description: Current Mode Multiplier
• Manufacturer: Intersil Corporation

Maximum bandwidth is maintained over a gain range of +6
to -16dB; bandwidth drops at lower gains. If wider gain range
with full bandwidth is required, two or more EL2082s can be
cascaded with the I
next.
The EL2082 can also be used with an I
circuit:
NOTE:
The EL2120 and EL2090 are suitable in this circuit but they
are compensated for 300
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 910
gain, or if R
acceptable.
1. With the EL2171, the EL2082 had ±15V supplies and the EL2171 required a 150 output load.
EL2171 (Note 1)
OPERATIONAL
AMPLIFIER
EL2020
EL2020
EL2130
EL2030
FIGURE 2. INVERTING EL2082 + OP-AMP
F
= 1k and an overall bandwidth of 25MHz were
GAIN = -
OUT
of one directly driving the I
V
------------------
GAIN
1V
POWER SUPPLIES
feedback resistors. R
8
----------------------------
R
±15V
±15V
±5V
±5V
±5V
IN
and R
R
+
F
95
F
reduced for a -1/3
V operational
IN
IN
would
R
1k
1k
1k
1k
2k
F
of the
EL2082
1.8k
910
910
910
910
R
IN
The circuit above gives a negative gain. The main concern of
this connection involves the total I
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 5MHz. A
typical cure is to add a capacitor C
This will reduce overall bandwidth, so a capacitor C
added to regain frequency response. The ratio C
made equal to R
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:
The EL2082 can also be used within an op-amp's feedback
loop:
With voltage-mode op-amps, the same concern about
capacitance at the summing node exists, so C
should be used. As before, current-feedback amplifiers tend
to solve the problem. However, in this circuit the inherent
FIGURE 3. EL2082 IN FEEDBACK INVERTING GAIN
R
1k
_
_
_
_
G
GAIN = -
BANDWIDTH
IN
114MHz
29MHz
34MHz
61MHz
82MHz
-3dB
/R
F
.
------------------
V
GAIN
1V
0.1dB BANDWIDTH PEAKING
R
---------------------------- -
F9
OUT
R
F
+
12.3MHz
I N
4.3MHz
5.3MHz
9.7MHz
11MHz
in the 2pF-10pF range.
95
and stray
F
and C
F
/C
IN
IN
1.2dB
can be
0
0
0
0
IN
is