OPA2658 Datasheet, PDF (10/14 Pages) Burr-Brown (TI) – Dual Wideband, Low Power, Current Feedback OPERATIONAL AMPLIFIER

SUPPLY VOLTAGES
The OPA2658 is nominally specified for operation using
±5V power supplies. A 10% tolerance on the supplies, or an
ECL –5.2V for the negative supply, is within the maximum
specified total supply voltage of 11V. Higher supply voltages
can break down internal junctions possibly leading to cata-
strophic failure. Single supply operation is possible as long as
common mode voltage constraints are observed. The com-
mon mode input and output voltage specifications can be
interpreted as a required headroom to the supply voltage.
Observing this input and output headroom requirement will
allow non-standard or single supply operation. Figure 3
shows one approach to single-supply operation.
+V_S
+V_S
R
V_S
2
V_OUT =
V_S
2
+ A_V V_AC
V_AC
R
1/2
OPA2658
R_OUT
R_L
402Ω
402Ω
FIGURE 3. Single Supply Operation.
ESD PROTECTION
ESD static damage has been well recognized for MOSFET
devices, but any semiconductor device deserves protection
from this potentially damaging source. This is particularly
true for very high speed, fine geometry processes.
ESD static damage can cause subtle changes in amplifier
input characteristics without necessarily destroying the de-
vice. In precision operational amplifiers, this may cause a
noticeable degradation of offset voltage and drift. Therefore,
static protection is strongly recommended when handling
the OPA2658.
OUTPUT DRIVE CAPABILITY
The OPA2658 has been optimized to drive 75Ω and 100Ω
resistive loads. The device can drive 2Vp-p into a 75Ω load.
This high-output drive capability makes the OPA2658 an
ideal choice for a wide range of RF, IF, and video applica-
tions. In many cases, additional buffer amplifiers are un-
needed.
Many demanding high-speed applications such as
ADC/DAC buffers require op amps with low wideband
output impedance. For example, low output impedance is
essential when driving the signal-dependent capacitances at
the inputs of flash A/D converters. As shown in Figure 4, the
100
10
1
0.1
G = +2
0.01
0.001
10k
100k
1M
10M
Frequency (Hz)
100M
FIGURE 4. Closed-Loop Output Impedance vs Frequency.
OPA2658 maintains very low closed-loop output impedance
over frequency. Closed-loop output impedance increases with
frequency since loop gain decreases with frequency.
THERMAL CONSIDERATIONS
The OPA2658 will not require heatsinking under most
operating conditions. Maximum desired junction tempera-
ture will set a maximum allowed internal power dissipation
as described below. In no case should the maximum junction
temperature be allowed to exceed 175°C.
The total internal power dissipation (P_D) is the sum of
quiescent (P_DQ) and additional power dissipated in the two
output stages (P_DL1 and P_DL2) while delivering load power.
Quiescent power is simply the specified no-load supply
current for both channels times the total supply voltage
across the part. P_DL1 and P_DL2 will depend on the required
output signals and loads. For grounded resistive loads, and
equal bipolar supplies, they would be at a maximum when
the outputs are fixed at a voltage equal to 1/2 either supply
voltage. Under this condition, P_DL1 = V_S2/(4•R_L1) where
R_L1 includes feedback network loading. P_DL2 is calculated
the same way.
Note that it is the power in the output stages, and not into the
loads, that determines internal power dissipation.
Operating junction temperature (T_J) is given by T_A + P_D θ_JA,
where T_A is the ambient temperature.
As an example, compute the maximum T_J for an OPA2658U
where both op amps are at G = +2, R_L = 100Ω, R_FB = 402Ω,
±V_S = ±5V, and at the specified maximum T_A = +85°C.
This gives:
P_DQ = (10V •17mA) = 170mW
P _DL1
=
P _{DL 2}
=
(5V)²
4 • (100Ω || 804Ω)
=
70mW
P_D = 170mW + 2 (70mW) = 310mW
T_J = 85° C + 0.310W •125° C / W = 124° C
®
OPA2658
10