AD840
HIGH SPEED DAC BUFFER CIRCUIT
OVERDRIVE RECOVERY
The AD840’s 100 ns settling time to 0.01% for a 10 V step
makes it well suited as an output buffer for high speed D/A con-
verters. Figure 25 shows the connections for producing a 0 to
+10.24 V output swing from the AD568 35 ns DAC. With the
AD568 in unbuffered voltage output mode, the AD840 is
placed in noninverting configuration. As a result of the 1 kΩ
span resistor provided internally in the AD568, the noise gain of
this topology is 10. Only 5 pF is required across the feedback
(span) resistor to optimize settling.
Figure 26 shows the overdrive recovery capability of the AD840.
Typical recovery time is 190 ns from negative overdrive and
350 ns from positive overdrive.
Figure 26. Overdrive Recovery
Figure 27. Overdrive Recovery Test Circuit
Figure 25. 0 V to +10.24 V DAC Output Buffer
OUTLINE DIMENSIONS
Dimensions shown in inches and (mm).
14-Pin Cerdip (Q) Package
14-Pin Plastic (N) Package
20-Pin LCC (E) Package
–8–
REV. C
ADI [ ADI ]
