Hardware Reference
In-Depth Information
Chunhua-Haiguang-Yan Universal biquads Figure 12.49 shows two universal
filtering circuits proposed by Chunhua et al. [ 128 ]. Each circuit uses two CCIIs with
multiple outputs (MO-CCIIs), one multiple output current-controlled current ampli-
fier (MO-CCCA), two grounded resistors and two grounded capacitors. Both the
circuits are capable to realize all five filtering functions. The filter parameters
ˉ 0 and Q 0 can be controlled independently by bias current of MO-CCCA.
Using the ideal port relations of MO-CCII and MO-CCCA, a routine analysis of
both the circuit yields:
I 1
sI 2 R 1 C 1 K
s 2 I 3 C 1 C 2 R 1 R 2
I 0 ¼
for Fig
:
12
:
49a
ð
12
:
175
Þ
1
þ
sC 1 R 1 K
þ
s 2 C 1 C 2 R 1 R 2
and
s 2 I 3 C 1 C 2 R 1 R 2
K
ð
I 1
sI 2 R 1 C 1 þ
Þ
I 0 ¼
for Fig
:
12
:
49b
ð
12
:
176
Þ
þ
sC 1 R 1 K
þ
s 2 C 1 C 2 R 1 R 2
1
where K is the current gain and is given by
I i
I B
2 I A
K
¼
ð
12
:
177
Þ
Both the circuits of Fig 12.49 were simulated in SPICE using the CMOS MOCC
implementation devised by Surakampontorn et al. [ 206 ]. The component values
were chosen to attain f o ¼
159 KHz, Q o ¼
1. The MSOFET model parameters were
taken from MOSIS based on 0.5
m CMOS technology. Figure 12.49c shows the
variability of the f o with respect to the resistors in the circuit, which confirm the
workability of the circuit.
μ
Senani ' s MISO-type CM biquad A universal MISO CM biquad employing all
grounded passive elements and only two dual output CCs (DOCCs) was presented
by Senani [ 131 ]. The proposed configuration is shown in Fig. 12.50 which realizes
all the basic generic filter responses providing explicit current outputs. Electronic
tunability of the filter parameters can also be accomplished by replacing the
resistors R 1 ,R 2 and R 3 by appropriate CMOS grounded resistors. The port charac-
teristics of DOCC are given by i y ¼
0, v x ¼
v y, i z+ ¼
+i x and i z- ¼
i x , a routine
circuit analysis gives an expression for I 0 in terms of input currents:
C 2 R 2 I 1 þ
I 3
I 2 s 2
s
R 1 C 2
1
1
C 1 R 3 C 2 R 2
þ
s
R 1 C 2
I 0 ¼
ð
12
:
178
Þ
1
1
C 1 C 2 R 3 R 2
s 2
þ
s
þ
The various filter functions can be realized from equation ( 12.183 ) as follows:
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