HA17431VPJ/PJ/PAJ/FPJ/FPAJ/PNAJ/UPA, HA17432UPA
In Figure 3, the following formulas are obtained:
Gain
G1 = G0 ≈ 50 dB to 60 dB (determined by shunt regulator)
G2
=
R5
R3
Corner frequencies
f1 = 1/(2π C1 G0 R3)
f2 = 1/(2π C1 R5)
G0 is the shunt regulator open-loop gain; this is given by the reciprocal of the reference voltage fluctuation
∆Vref/∆VKA, and is approximately 50 dB.
3. Practical Example
Consider the example of a photocoupler, with an internal light emitting diode VF = 1.05 V and IF = 2.5 mA, power
supply output voltage V2 = 5 V, and bias resistance R2 current of approximately 1/5 IF at 0.5 mA. If the shunt
regulator VK = 3 V, the following values are found.
R1 =
5V – 1.05V – 3V
2.5mA + 0.5mA
= 316(Ω) (330Ω from E24 series)
R2
=
1.05V
0.5mA
= 2.1(kΩ)
(2.2kΩ from E24 series)
Next, assume that R3 = R4 = 10 kΩ. This gives a 5 V output. If R5 = 3.3 kΩ and C1 = 0.022 µF, the following
values are found.
G2 = 3.3 kΩ / 10 kΩ = 0.33 times (–10 dB)
f1 = 1 / (2 × π × 0.022 µF × 316 × 10 kΩ) = 2.3 (Hz)
f2 = 1 / (2 × π × 0.022 µF × 3.3 kΩ) = 2.2 (kHz)
REJ03D0892-0100 Rev.1.00 Apr 03, 2007
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