MC3405
Figure 12. Window Comparator
VCC
∆V
10 k
Adjust
10 k
13
–
14
12 Amp 1
+
10 k
VCC
10 k
VC Adjust
VEE
10 k
10 k
9
–
8
10 Amp 2
+
VCC
5
4
3.0 k
–
7
6 Comp 2
+
11
VEE
3
–
1
2
Comp 1
+
vO
Vin
Figure 13. Squelch Circuit for AM or FM
C3
C1
R2
C2
13
Vin
–
14
R1
12
Amp 1
+
High Pass Filter
High Pass Filter
Given: Ao, Q, ωo = 2πfo
Choose: C = C1 = C2, a convenient value
Calculate:
R2
=
Q
ωoC
(2Ao + 1)
C3 = C
Ao
R1 =
Ao
QωoC(2Ao + 1)
3
–
1
2 Comp 1
C4
R3
+
VCC
100 k
Squelch
Threshold Adj
R3C4 > 5 Tin
Where : Tin is the period of Vin
Q = Quality Factor
Ao = High Frequency Gain
ωo = Break Frequency
VO
13
∆V
∆V
Vin
–13
VC
VCC
2.7 k
10
+
8
2.7 k
9 Amp 2
VAO
–
Rf
Ri
VAi
Switched Audio Stage
Gain of Audio Stage
ACI =
Rf
Ri
Figure 14. High/Low Limit Alarm
VCC
10 k
10 k
R6
R4
12
+
14
VCC
10 k
13 Amp 1
–
Oscillator
R5
R1
1.0 k
3
–
1
2 Comp 1
+
VCC
2.0 k
Rf 33 k
10
+
8
9 Amp 2
–
VO
Vi
R2
5
2.0 k
C 0.01 µF
–
7
1.0 k
6 Comp 2
+
VC
Hi/Low
R3
Limit Detector
VC
VCC
0
VIL VIH
Vi
VIL = VCC
R3
R1 + R2 + R3
VIH = VCC
R2 + R3
R1 + R2 + R3
Oscillator
If R4 = R5 = R6
f = 0.72/RfC
As shown, f = 2.2 kHz
VO will oscillate if VIH < Vi, or VIL > Vi
VO will be low if VIL < Vi < VIH
MOTOROLA ANALOG IC DEVICE DATA
7