(57) A Balun circuit for an integrated circuit having a small area and constructed using known semi-conductor fabrication processes. The balun circuit comprises two metallic strips (3,5) on a dielectric substrate (1) the strips (3,5) being substantially parallel to one another with a gap (7) there between and the second strip (5) having a length (21) to be equal to a quarter wavelength of the input signal, the values of the gap and strip widths (13,19) being predetermined such that the output impedances of the first and second metallic strips (3,5) respectively are substantially equal.