OPA4192_15 Datasheet, PDF (24/51 Pages) Texas Instruments – OPAx192 36-V, Precision, Rail-to-Rail Input/Output, Low Offset Voltage, Low Input Bias Current Op Amp with e-trim™

OPA192, OPA2192, OPA4192
SBOS620D – DECEMBER 2013 – REVISED SEPTEMBER 2015
www.ti.com
8.3 Feature Description
8.3.1 Input Protection Circuitry
The OPAx192 uses a unique input architecture to eliminate the need for input protection diodes but still provides
robust input protection under transient conditions. Conventional input diode protection schemes shown in
Figure 54 can be activated by fast transient step responses and can introduce signal distortion and settling time
delays because of alternate current paths, as shown in Figure 55. For low-gain circuits, these fast-ramping input
signals forward-bias back-to-back diodes, causing an increase in input current, and resulting in extended settling
time, as shown in Figure 56.
V+
V+
VIN+
VIN
36 V
OPA192
VOUT
VIN+
VIN
~0.7 V
VOUT
OPA192 Provides Full 36-V
V
Differential Input Range
Conventional Input Protection
V
Limits Differential Input Range
Figure 54. OPA192 Input Protection Does Not Limit Differential Input Capability
Vn = +10 V R_FILT
+10 V
C_FILT
Vn+1 = ±10 V R_FILT
±10 V
C_FILT
Input Low Pass Filter
S_n
C_S
R_{on_mux}
1
D
1
2
+10 V
~±9.3 V
C_D
S_n+1
R_{on_mux}
2
Vin±
C_S
I_{diode_transient}
~0.7 V
Vin+
±10 V
Vout
Simplified Mux Model
Buffer Amplifier
Figure 55. Back-to-Back Diodes Create Settling Issues
100
80
60
40
20
0
±20
±40
±60
±80
±100
0
Standard Input Diode Structure
Extends Settling Time
0.1% Settling = ±10 mV
OPA192 Input Structure
Offers Fast Settling
5 10 15 20 25 30 35 40 45 50 55 60
Time (s)
C040
Figure 56. OPA192 Protection Circuit Maintains Fast-Settling Transient Response
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