A transmitter having an integratable quadrature oscillator network for simultaneously producing a sine wave and a cosine wave. The digital direction of rotation (whether the frequency is positive or negative) input is slow rate limited (R, C3) and fed into a low gm transconductor (MOS1, MOS2) to softly switch between two pairs of transconductor amplifiers (TR1, TR2 and TR3, TR4) which together with two capacitors (C1, C2) form quadrature oscillators of opposite direction of rotation. By softly switching the quadrature oscillators out-of-band emissions are minimised in a subsequent mixing with a carrier signal to generate a frequency modulated signal.