28129 Parallax Inc, 28129 Datasheet - Page 141

• Manufacturer Part Number: 28129
• Description: TEXT BASIC ANALOG & DIGITAL
• Manufacturer: Parallax Inc
• Type: Programmingr

Specifications of 28129

• Style: Book
• Title: Basic Analog and Digital
• Contents: Basic Analog and Digital Text
• Product: Microcontroller Accessories
• Lead Free Status / RoHS Status: Not applicable / Not applicable

Important: This circuit must be isolated from other circuits. The input impedance of the
V(+) pin on the ADC0831 is very high, high enough to make it invisible to the RC
circuit. But if you tried to use this circuit to drive an LED-resistor circuit without the
buffer, all the charge that built up in the capacitor would exit through the LED and
resistor.
Try connecting a 10k
what happens when you try to send 3.25 volts with a load on the D/A converter.
Since the D/A
have enough time to discharge all the way to 0 volts.
If the program were set to carry out the
discharge very quickly
High input impedance: BASIC Stamp I/O pins set to input mode, op-amp input terminals,
and the ADC0831's Vin terminals all have an important aspect in common that makes them
invisible to other circuits. It's high input impedance.
The term impedance includes both resistance and capacitance. High input impedance
means that the resistance is huge, and there is a very small capacitance as well.
The impedance at the input terminals of these devices is so high that it fools the most
circuits into behaving as if the inputs to these devices are open circuits. So, for the most
part, you can connect the output of just about any circuit to these inputs.
On the other hand, we've seen how comparatively low resistance circuits such as a 10k
resistor or an LED circuit can drastically change the output of D/A circuits.
One advantage of many D/A converter integrated circuits is that they provide reliable,
buffered output
PWM
repeats itself without a pause in the program, the capacitor does not
resistor from the D/A converter output to Vss. Figure 7-7 shows
PWM
command only once, the capacitor would