ISL55020 Datasheet, PDF (8/11 Pages) Intersil Corporation – Wideband, Low Distortion, Differential Amplifier

ISL55020
V+ V-
V_IN+
R_T+
V_IN-
R_T-
V_CM
R_T-VCM
EN
R_F1
R_IN+
FB+V+
OUT+
I_N+
V-
R_G
VCM +1
R_IN-
I_N-
FB-
GND-
EN
OUT-
R_F2
GND-
R_S+
R_L+
R_S+
R_L-
V_OUT+
V_OUT -
FIGURE 18. BASIC APPLICATION CIRCUIT
Description of Operation and Application
Information
Product Description
The ISL55020 is a full differential Current Feedback
Amplifier (CFA) featuring wide bandwidth and low power.
The device contains a pair of high impedance differential
inputs and a pair of differential outputs. It can be used in any
combination of single/differential ended input/output
configurations. A wide bandwidth unity gain, common mode
amplifier with a 100MHz -3dB bandwidth (Figure 6) is
included to provide DC offset correction or common mode
signal injection to the differential output. The ISL55020 is
internally compensated for single-ended closed loop gain
(A_VS), differential closed gain (A_VD) of 2, or greater.
Connected in differential gain of 5 (single ended gain of ±2.5
and driving a 200Ω differential load, the ISL55020 has a -
3dB bandwidth of 300MHz. Driving a 200Ω differential load
at gain of 10, the bandwidth is about 200MHz (Figure 3). The
ISL55020 is available with a power down feature (EN) to
reduce the power while the amplifier is disabled.
Input, Output, and Supply Voltage Range
The ISL55020 is designed to operate with dual supplies over
a range of +/-2.25V to +/-6V and can also operate with a
single supply over the range of 4.5V to 12V. For single
supply operation, the V- and GND pins must be connected
together as close to the device as possible. The amplifiers
have an input common mode voltage range from -4.3V to
3.4V when operated from ±5V supplies. The differential
mode input range (DMIR) between the two inputs is from -
2.3V to +2.3V. The input voltage range at the VCM pin is
from -3.3V to 3.7V. If the input common mode or differential
mode signal is outside the above-specified ranges, the
output signal will be distorted.
The output of the ISL55020 can swing from -3.8V to +3.8V at
100Ω differential load at ±5V supply. As the load resistance
becomes lower, the output swing is reduced.
Single-ended, Differential and Common Mode Gain
Settings
The ISL55020 can be used as a single/differential ended to
differential/single converter. The voltage applied at VCM pin
sets the output common mode voltage and the common
mode gain is fixed at gain is one (A_VCM = 1).
The output differential voltage is given by the following:
V_OD = (V_IN+ - V_IN-) x (1 + 2R_F/R_G)
(EQ. 1)
Where:
R_F1 = R_F2 = R_F
The differential output gain (A_VD) is defined by the feedback
resistors according to the following
A_VD = 1 + 2R_F/R_G
(EQ. 2)
The single ended output voltage (V_OS) contains a common
mode component (V_CM) and a differential mode component
equal to one-half the differential output (V_OD/2)., and is
given by the following:
V_OS = V_OD/2 + V_CM = V_CM +(V_IN+ - V_IN-) x (0.5 + R_F/R_G) _{(EQ. 3)}
and the single-ended gain becomes:
A_VS = 0.5+ R_F/R_G
(EQ. 4)
8
FN6287.0
December 18, 2006