Define Voltage Source Multiplying DAC?

Voltage source multiplying DACs use a reference voltage which is switched in or out by the digital data.  The converter is so-named because it multiplies a certain gain value with a source voltage (Vcc in this case).  

Let us consider a 2-bit example. To transform 10 to analog, resistance R is switched in by digital control logic, and the resistor 2R is grounded.  The achievement of the circuit is R1/R that can be adjusted to an appropriate value. 

For the sake of the example, let R1 = R.  The overall gain of the circuit would then be unity, which would give an output of Vcc. The common conversion equation for this circuit is as follow:

 V_O = - [V_in * (R₁ / R) + V_in * (R₁ / 2R)]  

A 2-bit conversion table would be like this: