AND8054 Datasheet, PDF (14/28 Pages) ON Semiconductor – Designing RC Oscillator Circuits with Low Voltage Operational Amplifiers and Comparators for Precision Sensor Applications

Gain (dB)
ǒ Ǔ 20x log ₁₀
C3
C4
Fz1
+
1
2pR5C3
AND8054/D
Oscillation
Range
Assumptions
1. C3 u C4
2. C3 [ C4
3. R3 t R4 t R5
4.
R3
tt
R5
and
R4
[
R5
10
0
ǒ Ǔ 20x log ₁₀
R4
R3 ) R5
Fp1
+
1
2pR4C4
Fp2
+
1
2pR3C3
Frequency (Hz)
Figure 12. Bode Plot of Differentiator Amplifier A₃
Ratio Oscillator
Step 4: Verify LG . 1
Step 4 will be demonstrating using the single power supply limit circuit shown in Figure 26.
The design equations are listed below.
Assume:
1.) ^{V2 + VMax_Limit (i.e.|A2| + VMax_Limit)}
2.)
|A3|
+
C3
C4
Check:
1.) Is |LG| + A1 A2 A3 w VMax_Limit
ǒ Ǔ ǒ Ǔ +
1
2pfR1C1
(VMax_Limit)
C3
C4
w VMax_Limit
2.) Using the values shown in Figure 26,
ǒ Ǔ ǒ Ǔ 1
2p(16.5 kHz)(39 K W) (240 pF)
(VMax_Limit)
C3
C4
w VMax_Limit
ǒ Ǔ (1.03) (VMax_Limit)
C3
C4
w VMax_Limit
3.) Oscillation will be sustained if
ǒ Ǔ ^C3
C4
w
1
1.03
http://onsemi.com
14