Power Supply Specifications
Specified Voltage Range (VS)
Operating Voltage Range (VS)
Quiescent Current (IQ)
1
Specified and Operating Voltage Range (VS)
For 2.2V < VS < 5.5V data sheet
specifications will be met
For 2 < VS < 2.2V the op amp will still
function but all data sheet
specifications may not be met
i.e. Output Swing to Rail, AOL, etc may be
degraded
2
Quiescent Current (IQ)
+Vs
IQ
+
+
Vout
Real Op Amp
IQ
-Vs
Quiescent Current:
Supply Current to operate the op amp
Does NOT include load current
3
Temperature Range
Specifications
Specified Range
Operating Range
Thermal Resistance (QJA)
4
Specified and Operating Temperature Range
For -40C < TA < +125C data sheet
specifications will be met
For +125C < TA < +150C the op amp will still
function but all data sheet specifications
may not be met
i.e. Output Swing to Rail, Aol, etc may be
degraded
5
Thermal Resistance (QJA)
6
Thermal Resistance (QJA)
QJA will be used with ambient
temperature TA and internal
total power dissipation PD to
compute maximum op amp
junction temperature TJ
7
Thermal Model
PD = PIQ + POUT
PD = Total Power Dissipated
PIQ = Power Dissipated due to IQ
POUT = Power Dissipated in Output Stages
TJ
Thermal model with no heat sink
Analogous to an electrical circuit
PD
RθJA
TJ= PD( RθJA) + TA
T – is analogous to voltage
R – is analogous to resistance
TA
TA
P – is analogous to current
8
IQ Power Dissipation (PIQ)
PIQ = [+Vs - (-Vs) ] IQ
+Vs
IQ
+
+
Vout
Real Op Amp
IQ
-Vs
9
DC Normal Maximum Power
Dissipation in Output Stage (POUT)
+Vs
Vout =
IQ
+
Real Op Amp
+
1
2
Vs
Iout_DC
Vout
Vin
IQ
RL
POUT_DC =
Vs
2
4 RL
-Vs
RI
RF
10
DC Short Circuit Maximum Power
Dissipation in Output Stage (POUT)
POUT_SHORT = Vs Isc
+Vs
IQ
+
+
Real Op Amp
+
Isc
VF1
VG1
IQ
-Vs
RI
RF
11
AC Normal Maximum Power
Dissipation in Output Stage (POUT)
POUT_AC =
2 Vs
2
2
+Vs
IQ
RL
+
+
Vout peak =
2 Vs
Real Op Amp
+
Iout_AC
Vout
Vin
IQ
RL
Pc(Push-Pull) vs Vload for an AC Sinusoidal Signal
-Vs
P(Push Pull Output Transistors)
0.3
0.25
RI
RF
0.2
0.15
POUT_AC =
0.1
Vout peak =
2 Vs
2 Vs
2
2
RL
0.05
0
0
1
2
3
4
5
V(load) peak AC Sinusoidal Voltage
12
AC Normal Maximum Power
Dissipation in Output Stage (POUT)
Vcc 5
AC Maximum Power Dissipation Formula
based on symmetrical dual supplies
Vcc
To use formula for single supply circuits
set +Vs = +(Vcc/2) and -Vs = -(Vcc/2) as
shown.
IQ
+
+
Real Op Amp
Iout_AC
+
Vout
Vin
IQ
RL
+Vs 2.5
+Vs = (Vcc/2)
IQ
+
+
RI
RF
Real Op Amp
+
Iout_AC
Vout
Vin
IQ
RL
POUT_AC =
2 Vs
2
2
RL
-Vs 2.5
RI
RF
-Vs = -(Vcc/2)
13
Thank you!
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