9 Non-Inverting Programmable Gain Amplifier

Figure 9-1 displays an op amp in a non-inverting amplifier configuration. The main difference from the previous voltage follower configuration is the presence of the R2/R1 resistor divider in the negative feedback loop. The resistor divider allows for the upward scaling of the input signal. This adjustment can be done by programming the R2/R1 ratio, hence the name of Programmable Gain Amplifier (PGA).

Figure 9-1. Non-Inverting Programmable Gain Amplifier

The output voltage is given by the formula:

$V_{O U T} = (1 + \frac{R_{2}}{R_{1}}) V_{I N}$

The gain (amplification) of the configuration is given by the formula:

$G a i n = 1 + \frac{R_{2}}{R_{1}}$

As in the case of the voltage follower, the non-inverting programmable gain amplifier is applicable for coupling a high input impedance with a low output impedance. It is perfectly suited as an intermediary stage between a low voltage signal coupled to an ADC.