28128 Parallax Inc, 28128 Datasheet - Page 92

• Manufacturer Part Number: 28128
• Description: KIT BASIC ANALOG/DIGI PARTS ONLY
• Manufacturer: Parallax Inc

Specifications of 28128

• Accessory Type: ADC, DAC
• Product: Microcontroller Accessories
• For Use With/related Products: BASIC Stamp® 2 and Board of Education
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Figure 4-7 shows the D/A converter with an LED circuit added. The LED circuit is the
"load" that the D/A converter must "drive". Run a voltage sweep on this circuit, and fill
in the table below. Then try the voltage sweep using the output of the voltage follower in
as shown in Figure 4-8. Fill out the same table of voltage sweep information for this
second circuit, and compare the two. The voltage follower in Figure 4-7 is referred to as a
buffer. The LED circuit has no voltage follower to separate it from the resistive ladder
network. The LED is an "unbuffered" load for the D/A converter.
Decimal
00
01
02
03
04
05
06
07
08
09
10
11
12
13
14
15
Table 4-1:D/A Converter Output Without Buffer
Binary
0000
0001
0010
0011
0100
0101
0110
0111
1000
1001
1010
1011
1100
1101
1110
1111
DVM (volts)
___________
___________
___________
___________
___________
___________
___________
___________
___________
___________
___________
___________
___________
___________
___________
___________