Rev. 2.0, 11/00, page 736 of 1037
28.11.6
Filter Characteristics
(1) Lag-Lead Filter
A filter required for a servo loop is built in the hardware. This filter uses an IIR (Infinite
Impulse Response) type digital filter (another type of the digital filter is FIR, i.e. Finite
Impulse Response type). This digital filter circuit implements a lag-lead filter, as shown in
figure 28.40.
R1
R2
C
+
INPUT
OUTPUT
Figure 28.40 Lag-lead Filter
The transfer function G (S) is expressed by the following equation.
S
1+
2
π
f
2
Transfer function G (S) =
S
1+
2
π
f
1
f
1
=1/2
π
C (R1+R2)
f
2
=1/2
π
CR2
Summary of Contents for Hitachi H8S/2191
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