OPA699IDG4 Datasheet, PDF (18/31 Pages) Texas Instruments – Wideband, High Gain VOLTAGE LIMITING AMPLIFIER

LIMITED OUTPUT, DIFFERENTIAL ADC INPUT DRIVER
Figure 7 shows a differential ADC driver that takes advan-
tage of the OPA699 limiters to protect the input of the ADC.
Two OPA699s are used. The first one is an inverting configu-
ration at a gain of –2. The second one is in a noninverting
configuration at a gain of +2. Refer to the section, Low Gain
Compensation for Improved SFDR, for a discussion of stabil-
ity issues of the OPA699 operating at a gain less than 4.
Each amplifier is swinging 2V_PP providing a 4V_PP differential
signal to drive the input of the ADC. Limiters have been set
100mV away from the magnitude of each amplifier maximum
signal to provide input protection for the ADC while maintain-
ing an acceptable distortion level.
PRECISION HALF WAVE RECTIFIER
Figure 8 shows a half wave rectifier with outstanding preci-
sion and speed. V_H (pin 8) will default to a 3.5 typically if left
open, while the negative limit is set to ground.
The gain for the circuit in Figure 8 is set at +6. Figure 9 shows
input and output for ±0.5V 100MHz input.
3.5
Output
3.0
2.5
2.0
1.5
1.0
0.5
0
–0.5
Input
–1.0
Time (5ns/div)
FIGURE 9. 100MHz Sinewave Rectified.
VERY HIGH-SPEED SCHMITT TRIGGER
Figure 10 shows a very high-speed Schmitt Trigger. The
output levels are precisely defined, and the switching time is
exceptional. The output voltage swings between V_H and V_L.
50Ω
Source
75Ω
V_IN
150Ω
+V_S = +5V
27
V_O = Open
8
OPA699 ⁶
V_O
3
5
4
750Ω
–V_S = –5V
FIGURE 8. Precision Half-Wave Rectifier.
V_REF
V_IN
R₁
200Ω
R₃
200Ω
R₂
402Ω
+2V
V_H
OPA699
V_L
–2V
V_OUT
FIGURE 10. Very High-Speed Schmitt Trigger.
V_IN = 200mV_PP
100Ω
100Ω
+5V
+1.1V
OPA699
–5V
1kΩ
–1.1V
24.9Ω 0.01µF
+5V
OPA699
+1.1V
4V_PP
24.9Ω ^0.01µF
–5V
900Ω
–1.1V
10pF
1kΩ
1kΩ
10pF
IN
ADC
V_CM
IN
100Ω
FIGURE 7. Single to Differential AC-Coupled, High Gain Output Limited ADC Driver.
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OPA699
SBOS261D