Second Generation Controlled Current Conveyors (CCCII) and Their Applications - Current Conveyors: Variants, Applications and Hardware Implementations - page 253

current repeater such that, as shown in the diagram, all the bias currents are equal to
I o except one which has been arranged to be 2I 0 . From the various currents marked
on the diagram, it can be easily worked out that I y ¼ 0, V x ¼ V y +R x i x where

R x ¼ i x .

This circuit was implemented in 0.8

V T /I 0 and that i z ¼

μ

m Bi-CMOS technology which incorpo-
rates vertical NPN and lateral PNP transistors with transition frequencies (f T ) of the
order of 11 GHz and 500 MHz, respectively. For the N-MOS transistors W/L was
taken as 40 m whereas for all the P-MOS transistors the aspect ratio was

20 μ m/1.1 μ m except for one it was required to supply a current of 2I 0 in which case
the aspect ratio was 40 μ m/1.1 μ m. It was found that with these values, the CCCII
when biased by

μ m/3 μ

2.2 V supply and I 0 ¼ 500 μ A, was characterized by R x ¼ 80 ʩ

and 3 dB bandwidth of the current gain and voltage gain was more than 2 GHz.
The significant advantages accrued in circuit design employing CCCIIs can be
summarized as follows:

(i) All the functions can be realized by using only CCCIIs and capacitors; no
external resistors are needed. Due to the complete absence of the resistors and
availability of electronic-controllability of the parameters of interest, CCCII-
based circuits are highly suitable for IC implementation.
(ii) The parameters of interest of the realized functional circuits can be controlled
by varying external DC bias currents.
(iii) CCCII-based circuits can be operated from low power supply voltages, typi-
cally 2.5 V DC, in contrast to op-amp circuits which typically require 6V

15 V DC power supplies.
(iv) Bipolar CCCIIs based upon the four-transistor mixed translinear cell have
much higher slew rate typically, several hundred V/

to

s as compared to
op-amps (such as uA741) having a very modest 0.5 V/

μ

s. Thus, CCCII-
based circuits can be operated at relatively much higher frequencies.
Although a majority of the applications described in the following deal with
bipolar CCCIIs, however, there are a number of applications which are based upon
CMOS CCCIIs in which case the dependence of the various parameters on the
external bias currents is different. It may be noted that R x is inversely proportional
to I B in case of the bipolar CCCII whereas it is inversely proportional to the square
root of I B in case of CMOS CCCIIs.

μ

9.3 Grounded and Floating Current-Controlled Positive/
Negative Resistance Realization

If terminal-Y is grounded and terminal-Z is also grounded as shown in Fig. 9.7 , the
circuit realizes a current-controlled resistance. Looking into terminal-X, the equiv-
alent input impedance is then found to be R in ¼

V T

2 I B .As an example, if V T is taken as