A transconductance circuit has an input terminal (VIN) and an output terminal (Out), a first current source (4) having a gate connected to said input terminal (VIN); and a second current source (5), in parallel with said first current source, and having a higher transconductance and a wider dynamic range than the first current source. The current sources are configured so that at a low input voltage only the first current source (4) is on. A voltage drop circuit provides a lower bias voltage for the second current source than for the first current source.