2.5 Tri-level Voltage Detector
stops and the op amp responds open loop. The design equa-
tion directly preceding Figure 14, shows how to determine
the clamping range. The equation solves for the input volt-
age band on each side GND. The mid-range is twice this
voltage band.
The tri-level voltage detector of Figure 13 provides a type of
window comparator function. It detects three different input
voltage ranges: Min-range, Mid-range, and Max-range. The
output voltage (VO) is at VCC for the Min-range. VO is
clamped at GND for the Mid-range. For the Max-range, VO is
at Vee. Figure 14 shows a VO vs. VI oscilloscope photo per
the circuit of Figure 13.
Its operation is as follows: VI deviating from GND, causes
the diode bridge to absorb IIN to maintain a clamped condi-
tion (VO= 0V). Eventually, IIN reaches the bias limit of the di-
ode bridge. When this limit is reached, the clamping effect
DS100128-89
|
∆v
|
∆v
|
OV
+V
IN
DS100128-35
-V
IN
OV
FIGURE 14. X, Y Oscilloscope Trace showing VOUT vs
DS100128-34
VIN per the Circuit of Figure 13
FIGURE 13. Tri-level Voltage Detector
15
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