Hardware Reference
In-Depth Information
where R x represents the parasitic resistance at X-terminal, g m1 ,g m2 are the
transconductances from the Z-terminal to -O 1 and O 2 terminal respectively.
When DVCCCTA is implemented in CMOS technology, the parasitic resistance
R x and the two transconductance parameters will be given by:
r
1
8 k 1 I B 1
¼ ʼ n C ox W
L
and
where k 1 ¼ ʼ p C ox W
L
R x ¼
ð
13
:
34
Þ
p
k 2 I B 2
where k 2 ¼ ʼ n C ox W
L
g m 1 ¼
ð
13
:
35
Þ
p
k 3 I B 3
where k 3 ¼ ʼ n C ox W
g m 2 ¼
ð
13
:
36
Þ
L
From the CE, CO and FO can be obtained as:
CO
:
g m 1 R x
1or k 2 I B 2 <
8 k 1 I B 1
ð
13
:
37
Þ
r
g m 2
C 1 C 2 R x
1 = 4
ð
8 k 1 k 3 I B 1 I B 3
Þ
FO
: ω 0 ¼
¼
ð
13
:
38
Þ
1 = 2
ð
C 1 C 2
Þ
Hence, it is seen that CO and FO are independently electronically-variable by I B2
(g m1 ) and I B3 (g m2 ) respectively. The various output voltages and currents are
related by the following expressions:
j ω 0 C 1
g m 2
V 02 ¼
V 01
ð
13
:
39
Þ
j ω 0 C 2
g m 2
I 02 ¼
I 01
ð
13
:
40
Þ
Thus, from the above equations, it is clear that both voltage output signals and
current output signals are in quadrature.
The workability of the proposed circuit was verified by the authors of [ 43 ]bya
CMOS DVCCCTA devised by them using which the proposed QO was simulated
in SPICE using 0.25
μ
m TSMS CMOS technology. The component values were
chosen to give oscillation frequency of 1.1 MHz. Figure 13.11b shows the building
up of the oscillations, Fig. 13.11c shows the steady state waveforms for the CM and
VM outputs while Fig. 13.11d shows the frequency spectra of the CM and VM
output waveforms. THE THD was found to be 3 % and 5 % respectively for VM
and CM outputs. These results confirm the practical workability of the proposed QO
circuit of Fig. 13.11 .
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