Nonlinear Applications of CCs - Current Conveyors: Variants, Applications and Hardware Implementations - page 221

(b) Full wave rectifier: If we choose the input signal current such that | I in | >> 2 I 0 ,

then from equations for I 1 and I 2 it turns outs that

I 1 0 and I 2 2 I in , for I in > 0 ð 8 : 14 Þ

I 1 2 I in and I 2 0 for I in < 0 ð 8 : 15 Þ

From the above, it follows that the output current is given by I out ¼ 2| I in | and the

circuit, therefore, functions as a full wave rectifier.

8.4 Multipliers, Dividers, Squarers and Square Rooters

Liu et al. demonstrated in [ 1 ] that using current conveyors in conjunction with
MOSFETs interesting circuits can be obtained for realizing fully integrable
non-linear building blocks such as multipliers, dividers, Squarers, square rooters
and vector submission circuits. In all such circuits, the MOSFET is generally
operated in triode region.
In the circuit of the Fig. 8.9a if the two MOSFETs are assumed to be operating in
the non- saturated region then the current output of the multiplier can be expressed as:

W
2 L ʼ s C ox

I 0 ¼ 2KV 1 V 2 whereK ¼ ð 8 : 16 Þ

The operational range of this circuit is governed by the following constraint:

V 1 min V G þ ½ V 2 V TH , V G V TH ð 8 : 17 Þ

It is worth mentioning that if we exchange the gate voltages of the two MOSFETs,
the resulting circuit will still be a multiplier with I 0 ¼ 2KV 1 V 2 .

Using the multiplier proposed above an analog divider is obtained from the
configuration of Fig. 8.10 . A routine analysis of this circuit reveals that the output
voltage of this circuit is given by:

1
2 KR

V 1
V 2

V 0 ¼ ð 8 : 18 Þ

An alternative CC-based voltage-to-current converter using a MOS resistive circuit,
containing four MOSFETs, is shown in Fig. 8.11 .
Assuming the MOSFETs to be matched and operating in triode region, it turns
out that the output current I 0 of this circuit is given by:

I 0 ¼ 2 KV GA ð V GB Þ ð V in 1 V in 2 Þ ð 8 : 19 Þ