A single-stage differential operational amplifier comprising: an input stage formed by a pair of input transistors , having control terminals connected to a first and respectively second input (IN+, IN-) of said operational amplifier , first conduction terminals coupled to a first and respectively second output (OUT-, OUT+) of said operational amplifier and second conduction terminals designed to receive a biasing current (I b ); an output stage formed by a pair of output transistors , in diode configuration, having control terminals, each designed to be coupled to a corresponding first conduction terminal, connected to the first and respectively second output (OUT - , OUT + ) of said operational amplifier , and second conduction terminals connected to a reference line (gnd), characterized by further comprising: a coupling stage interposed between the first conduction terminals of said output transistors and said first and respectively second output (OUT-, OUT+) and configured to define a small-signal gain value (G) of said operational amplifier; wherein said coupling stage comprises a first and a second coupling transistor , having control terminals connected together for receiving a first biasing voltage (V b1 ), first conduction terminals connected to a respective one of said first and second outputs (OUT-, OUT+) and second conduction terminals coupled to the first conduction terminals of said output transistors and directly connected together by a connection line . an input stage formed by a pair of input transistors , having control terminals connected to a first and respectively second input (IN+, IN-) of said operational amplifier , first conduction terminals coupled to a first and respectively second output (OUT-, OUT+) of said operational amplifier and second conduction terminals designed to receive a biasing current (I b ); an output stage formed by a pair of output transistors , in diode configuration, having control terminals, each designed to be coupled to a corresponding first conduction terminal, connected to the first and respectively second output (OUT - , OUT + ) of said operational amplifier , and second conduction terminals connected to a reference line (gnd), characterized by further comprising: a coupling stage interposed between the first conduction terminals of said output transistors and said first and respectively second output (OUT-, OUT+) and configured to define a small-signal gain value (G) of said operational amplifier; wherein said coupling stage comprises a first and a second coupling transistor , having control terminals connected together for receiving a first biasing voltage (V b1 ), first conduction terminals connected to a respective one of said first and second outputs (OUT-, OUT+) and second conduction terminals coupled to the first conduction terminals of said output transistors and directly connected together by a connection line . a coupling stage interposed between the first conduction terminals of said output transistors and said first and respectively second output (OUT-, OUT+) and configured to define a small-signal gain value (G) of said operational amplifier; wherein said coupling stage comprises a first and a second coupling transistor , having control terminals connected together for receiving a first biasing voltage (V b1 ), first conduction terminals connected to a respective one of said first and second outputs (OUT-, OUT+) and second conduction terminals coupled to the first conduction terminals of said output transistors and directly connected together by a connection line . <EOS>