Hardware Reference
In-Depth Information
Fig. 3.21 PA
630 configured as CCII [ 19 ]
and arranged to realize
a noninverting amplifier
11
+V
Q 8
Q 7
Q 3
Q 4
Q 2
Q 3
10
7
5
Q 1
Out
R 2
6
R 1
R 4
R 3
In
9
R 5
Q 5
Q 6
8
−V
The main characteristic features of this IC are accuracy of 0.5 %, the bandwidth
of CC as 80 MHz, CC distortion 0.02 % with buffer amplifier bandwidth of
50 MHz.
When PA630 was announced it was enthusiastically welcomed by the academic
community particularly those involved in current conveyor research however, the
practicing engineers were still hesitant in using these devices possibly due to their
unfamiliarity with current mode circuits and techniques.
In retrospection, it appears that after the emergence of more versatile and easy to
use AD844 employing a CCII+ along with a voltage buffer, PA630 perhaps did not
receive so much attention in literature possibly due to the cumbersome DC bias
arrangements needed and/or the difficulty of using it as standalone three-terminal
CCI or CCII.
3.3.3 AD844 from Analog Devices
The current feedback operational amplifier (CFOA) AD844 from Analog Devices is
composed of a translinear second generation CC (CCII+) based upon a four
transistor mixed translinear cell followed by a translinear voltage buffer (see
Fig. 3.22a ) for the block diagram of the internal circuit and Fig. 3.22b for its
transistor level implementation. Thus, AD844 is characterized by the following
terminal equations: i y ¼ 0, v x ¼ v y ,i z ¼ i x and v w ¼ v z .
 
Search WWH ::




Custom Search