This is a simple
example of using VBA for electronic design EE_Resistor_Divider.xls. You could ask - why use a
VBA function at all? But, even in this case, VBA makes analysis a little
easier to explore. Here's the divider circuit.
The gain (or, attenuation) of
this circuit is given by
K = R2 / (R1 + R2)
Let's create a simple VBA function to perform
this calculation (See VBA Basics).
' Gain of resistor divider
K_Rdiv1 = R2
/ (R2 + R1)
To see the VBA code hit ALT-F11
and double click on the Modules > Module1 in the VBA Project window. This
opens the code window for this module.
For this example, the divider is creating a precision
+5V reference from an available +10V reference. The +5V level is used as a reference
voltage for an ADC. But how accurate is this +5V level? Let's calculate the
output given ideal components and then given initial tolerances of the
+10V and resistors R1 and R2.