OPA684_15 Datasheet, PDF (1/31 Pages) Texas Instruments – Low-Power, Current Feedback OPERATIONAL AMPLIFIER

OPA684
OPA684
OPA684
SBOS219D – OCTOBER 2001 – REVISED JUNE 2009
Low-Power, Current Feedback
OPERATIONAL AMPLIFIER With Disable
FEATURES
q MINIMAL BANDWIDTH CHANGE VERSUS GAIN
q > 120MHz BANDWIDTH TO GAIN > +10
q LOW DISTORTION: < –78dBc at 5MHz
q HIGH OUTPUT CURRENT: 120mA
q SINGLE +5V TO +12V SUPPLY OPERATION
q DUAL ±2.5 TO ±6.0V SUPPLY OPERATION
q LOW SUPPLY CURRENT: 1.7mA
q LOW SHUTDOWN CURRENT: 100µA
APPLICATIONS
q LOW-POWER BROADCAST VIDEO DRIVERS
q EQUALIZING FILTERS
q SAW FILTER HIGH GAIN POST AMPLIFIERS
q MULTICHANNEL SUMMING AMPLIFIERS
q PROFESSIONAL CAMERAS
q ADC INPUT DRIVERS
DESCRIPTION
The OPA684 provides a new level of performance in low-power,
wideband, current-feedback (CFB) amplifiers. This CFB_plus ampli-
fier is the first to use an internally closed-loop input buffer stage that
enhances performance significantly over earlier low-power CFB
amplifiers. While retaining the benefits of very low power operation,
this new architecture provides many of the benefits of a more ideal
CFB amplifier. The closed-loop input stage buffer gives a very low
and linearized impedance path at the inverting input to sense the
feedback error current. This improved inverting input impedance
retains exceptional bandwidth to much higher gains and improves
harmonic distortion over earlier solutions limited by inverting input
linearity. Beyond simple high-gain applications, the OPA684 CFB_plus
amplifier permits the gain setting element to be set with consider-
able freedom from amplifier bandwidth interaction. This allows
frequency response peaking elements to be added, multiple input
inverting summing circuits to have greater bandwidth, and low-
power line drivers to meet the demanding requirements of studio
cameras and broadcast video.
The output capability of the OPA684 also sets a new mark in
performance for low-power current feedback amplifiers. Delivering
a full ±4V_PP swing on ±5V supplies, the OPA684 also has the
output current to support this swing into a 100Ω load. This minimal
output headroom requirement is complemented by a similar 1.2V
input stage headroom giving exceptional capability for single +5V
operation.
The OPA684’s low 1.7mA supply current is precisely trimmed at
25°C. This trim, along with low shift over temperature and supply
voltage, gives a very robust design over a wide range of operating
conditions. System power may be further reduced by using the
optional disable control pin. Leaving this disable pin open, or holding
it HIGH, gives normal operation. If pulled LOW, the OPA684 supply
current drops to less than 100µA while the I/O pins go to a high
impedance state.
V+
+
V_O
V–
I_ERR
Z_(S) I_ERR
R_F
R_G
Low-Power
Amplifier
Patent Pending
3
0
–3
–6
–9
–12
–15
–18
–21
R_F = 1kΩ
10
BW (MHz) vs GAIN
G=2
G=5
G = 10
G = 20
G = 50
G = 100
100
200
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PRODUCTION DATA information is current as of publication date.
Products conform to specifications per the terms of Texas Instruments
standard warranty. Production processing does not necessarily include
testing of all parameters.
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