CMOS Implementations of Current Conveyors - Current Conveyors: Variants, Applications and Hardware Implementations - page 74

+V DD

M b1 M 4 M 11

M 3

M 13 M 15

R bias

Z

M 7

M 6

M 1

M 2

Y

M 8c

M 9c

X

M 14

M 10

M 12

M 5

M 8 M 9

M b2

M b3

−V SS

Fig. 4.14 A bulk-driven CCII proposed by Khateb et al. (Adapted from [ 60 ] © 2011 Elsevier)

circuit exhibited the power consumption of 64 ʼ W, R X ¼ 27 Ω and R Z ||C Z of the

order of 0.89 M Ω ||40 fF.

4.15 Wide-band High Performance Current Conveyor

Arslan et al. [ 63 ] proposed a wide band high performance architecture which
consisted of an improved voltage follower stage which employs two source fol-
lowers along with a local feedback to obtain reduced equivalent impedance (see
Fig. 4.15 ).
The expression for the equivalent resistance looking into port-X is given by:

1
g m 11 g m 20 r o 11 1

1
g m 12 g m 21 r o 12 1

R X ¼ ð 4 : 13 Þ

ð þ g m 10 r o = 2 Þ ð þ g m 9 r o = 2 Þ

The output of the improved voltage follower stage is put to a current follower
consisting M 6 and M 19 which senses the current flowing through X-port and
copies it to the high impedance Z-port. Between ports X and Z, the current gain

ʱ

is given by:

g m 6, 19
g m 20, 21

ð W = L Þ 6, 19

i Z
i X

ʱ ¼ ð 4 : 14 Þ

ð W = L Þ 20 , 21

With the matching of the MOSFET M 6 with M 20 and that of M 19 with M 21 , ʱ is very

close to unity.
On the other hand, the equivalent resistance seen at the output port is R Z ¼ r 06 ||

r 019. SPICE simulation results, with CMOS circuit biased with 1.65 V, exhibit