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OPA454 Datasheet, PDF (19/36 Pages) Texas Instruments – High-Voltage (100V), High-Current (50mA) OPERATIONAL AMPLIFIERS, G = 1 Stable
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OPA454
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OPEN-LOOP GAIN LINEARITY
Figure 65 shows the nonlinear relationship of AOL and
output voltage. As Figure 65 shows, open-loop gain is
lower with positive output voltage levels compared to
negative voltage levels. Specifications in the
Electrical Characteristics table are based upon the
average gain measured at both output extremes.
AOL is a Function of VOUT and ILOAD
TP = +25°C
RL = 1880W, 1mV/div
RL = 900W, 2mV/div
74dB 89dB
RL = 4.87kW, 200mV/div
106dB
-50 -40 -30 -20 -10 0 10 20 30 40 50
Output Voltage (V)
Figure 65. Differential Input Voltage (+IN to –IN)
versus Output Voltage
Inverting Response
Measured Here, V1
R2
R1
10kW
SBOS391 – DECEMBER 2007
SETTLING TIME
The circuit in Figure 66 is used to measure the
settling time response. The left half of the circuit is a
standard, false-summing junction test circuit used for
settling time and open-loop gain measurement. R1
and R2 provide the gain and allow for measurement
without connecting a scope probe directly to the
summing junction, which can disturb proper op amp
function by causing oscillation.
The right half of the circuit looks at the combination of
both inverting and noninverting responses. R5 and R6
remove the large step response. The remaining
voltage at V2 shows the small-signal settling time that
is centered on zero. This test circuit can be used for
incoming inspection, real-time measurement, or in
designing compensation circuits in system
applications.
Table 2. Settling Time Measurement Circuit
Configuration Using Different Gain Settings for
Figure 66
GAIN
COMPONENT
1
5
10
R1 (Ω)
10k
2k
1k
R3 (Ω)
10k
2k
1k
R7 (Ω)
10k
4k
9k
R8 (Ω)
∞
1k
1k
VIN (VPP)
20
16
8
R4
Combination of Both
R3
10kW
Inverting and
R7
R8
Noninverting Responses, V2
-IN
VOUT
OPA454
+IN
A1
R5
10kW
R6
10kW
-IN
VOUT
OPA454
A2
+IN
VIN
Figure 66. Settling Time Test Measurement Circuit
Copyright © 2007, Texas Instruments Incorporated
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