AND8054 Datasheet, PDF (8/28 Pages) ON Semiconductor – Designing RC Oscillator Circuits with Low Voltage Operational Amplifiers and Comparators for Precision Sensor Applications

AND8054/D
ABSOLUTE OSCILLATOR DESIGN EQUATIONS
C4
C1
R1
– ^A1
R2
+
V₁
C2
– ^A2
+
R3
V₂
R4
– ^A3
+
V₃
Without C₄
A2
+
*
1
sR2C2
A3
+
*
R4
R3
V₁
V₂
V₃
A1
+
*
1
sR1C1
With C₄
A2
+
*
1
sR2C2
V₁
ƪǒ Ǔǒ Ǔƫ A3 + *
R4
R3
1
sR4C4 ) 1
V₃
V₂
A1
+
*
1
sR1C1
Figure 10. Absolute Oscillator Signal Flow Diagrams
Absolute Oscillator (without C₄)
Step 1: Find LG and Ds
The loop gain is found by breaking the loop and inserting a “test’’ voltage into the input.
V_TEST
A1
+
–
1
sR1C1
A2
+
–
1
sR2C2
V₁
A3
+
–
R4
R3
V₂
V_OUT
V₃
LG
+
VOUT
VTEST
+
A1
A2
A3
ǒ Ǔǒ Ǔǒ Ǔ Ds
+
N(s)
D(s)
+
1
*
LG
+
1
*
–
1
sR1C1
–
1
sR2C2
–
R4
R3
+
1
)
R4
s2R1R2R3C1C2
+
s2
)
R4
R1R2R3C1C2
+
s2R1R2R3C1C2 ) R4
s2R1R2R3C1C2
N(s) + s2R1R2R3C1C2 ) R4
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