Single-Ended vs Fully Differential Op Amps

This page covers the characteristics of Single-Ended Op Amps and Fully Differential Op Amps. It also touches upon Single Ended to Differential Conversion Operational Amplifier circuits.

As shown in Figure 1, single-ended Op-Amps have two inputs: positive and negative. They produce a single output, which is referenced to the system ground (GND).

Differential op-amps also have two power supply inputs, connected to positive and negative voltages. The crucial difference is that the output is fully differential, with one positive and one negative output. These outputs are differential, mirroring the nature of the inputs. The output voltages are equal in magnitude but opposite in polarity.

Single Ended to Differential Conversion

Figure 2 illustrates a single-ended to differential conversion circuit. This type of conversion becomes necessary when connecting an op-amplifier to a differential input of an ADC (Analog-to-Digital Converter).

The circuit on the left is referred to as an inverting amplifier, while the circuit on the right is a non-inverting amplifier. This naming convention depends on where the input signal is applied.

The gain of this single-ended to differential stage can be expressed as:

$Vo/Vi = Rf/Rg$