15.01.2013 Views

U. Glaeser

U. Glaeser

U. Glaeser

SHOW MORE
SHOW LESS

You also want an ePaper? Increase the reach of your titles

YUMPU automatically turns print PDFs into web optimized ePapers that Google loves.

FIGURE 11.11 Current-mode CMOS quaternary latch output waveforms: (a) Quaternary latch output and φ<br />

holding a ZERO, (b) Quaternary latch output and φ holding a ONE, (c) Quaternary latch output and φ holding a<br />

TWO, and (d) Quaternary latch output and φ holding a THREE.<br />

on a standard prototyping board. The waveforms in Fig. 11.11 show a sequence of HOLD operations at<br />

times necessary to hold each of the four possible values of the output. In each photo, the pulse in the<br />

lower trace is φ,<br />

which goes HIGH to HOLD the value of the output signal at that time. SETUP and<br />

HOLD times have been inferred from measured experimental data to be about 10 ns for single level<br />

transitions and about 35 ns for ZERO-THREE and THREE-ZERO transitions.<br />

Current-Mode CMOS Latched Quaternary Logic Full Adder Circuit<br />

The current-mode CMOS latched QFA circuit is described with the aid of the block diagram in Fig. 11.12.<br />

The single output quaternary quantizer shown in Fig. 11.9 is replaced by a modified QFA circuit that<br />

serves as the quantizer, creating the feedback current and the quaternary full adder outputs. Again, the<br />

latched QFA circuit is in the FOLLOW mode when φ is HIGH and φ<br />

is LOW. The circuit is in the HOLD<br />

© 2002 by CRC Press LLC

Hooray! Your file is uploaded and ready to be published.

Saved successfully!

Ooh no, something went wrong!