OPA2662 Datasheet, PDF (12/18 Pages) Burr-Brown (TI) – Dual, Wide Bandwidth OPERATIONAL TRANSCONDUCTANCE AMPLIFIER

HARMONIC DISTORTION
vs TOTAL QUIESCENT CURRENT
–20
2nd, 8mA
3rd, 8mA
–30
3rd, 17mA
–40
–50
2nd, 17mA
2nd, 34mA
3rd, 34mA
–60
1.0M
3.0M
10M
30M
Frequency (Hz)
FIGURE 5. Harmonic Distortion.
100M
BASIC CONNECTIONS
Shown in Figure 6 are the basic connections for the
OPA2662’s standard operation. Most of these connections
are not shown in subsequent circuit diagrams for better
clarification. Power supply bypass capacitors should be
located as close as possible to the device pins. Solid tanta-
lum capacitors are generally the better choice. For further
details see the “Circuit Layout” section.
ENABLE INPUTS
Switching stages compatible to TTL logic levels are pro-
vided for each OTA to switch the corresponding voltage-
controlled current source on within 30ns, and off within
200ns at full output power (I_OUT = ±75mA). This enable
feature allows multiplexing and demultiplexing, or a shut-
down mode, when the device is not in use. If the EN-input
is connected to ground or a digital “Low” is applied to it, the
collector (C) and emitter (E) pins are switched in the high-
impedance mode. When the EN-input is connected to +5V
(+V_CC) or a digital “High” is applied to it, the corresponding
OTA operates at the adjusted quiescent current. The initial
setting for the enable pins is that they are connected to the
positive supply as shown in Figure 6.
THERMAL CONSIDERATIONS
The performance of the OPA2662 is dependent on the total
quiescent current which can be externally adjusted over a
wide range. As shown later, the distortion will reduce when
setting the OTAs for higher quiescent current. For a reliable
operation, some thermal considerations should be made. The
total power dissipation consists of two separate terms:
a) the quiescent power dissipation, P_DQ
P _DQ
=
+ V _CC
•
I
+
Q
+
V _CC
• I_Q–
(1)
b) the power dissipation in the output transistors, P_DO
( ) P_DO = V_OUT – V_CC • I_OUT
(2)
Equations 1 and 2 can be used in conjunction with the
OPA2662’s absolute maximum rating of the junction tem-
perature for a save operation.
T_J = T_A + (P_DQ + P_DO) • θ_JA
(3)
+
2.2µF
10nF
470pF
+5V
V_IN1
V_IN2
100Ω
R_Q(1)
100Ω
1
+V_CC
2
B₁
3
EN₁
4
GND
5
I_Q Adjust
EN₂ ⁶
B₂ ⁷
OTA1
Logic
PTAT
Supply
Logic
OTA2
–5V
8
–V_CC
OPA2662
NOTE: (1) R_Q = 750Ω set roughly, I_Q = ±17mA.
2.2µF
+
10nF
FIGURE 6. Basic Connections.
OPA2662
12
16
+V_CCOUT
50Ω
15 _E1
R_E1
14 _C1
13 ^NC
12 NC
11 _C2
50Ω
10
E₂
R_E2
9
–V_{CC OUT}
470pF
I_OUT1
I_OUT2